Anyone know about the Polaris 380 pressure-side pool cleaner? I Picked up an old used non-working Polaris 380 pressure side wheeled pool cleaner.

[Gary Davis]

Does anyone here have practical experience with the Polaris 380 pressure-side pool cleaner?

At a garage sale I picked up this Polaris 380 pressure-side pool cleaner. Lady who sold it said her late husband used it but it was probably broken.
And it is. It doesn't seem to have any missing parts from the outside (and she gave me a box of additional parts); but it's not moving or suctioning up when I put a 1.6HP 5000gph sump pump on the pressure side.

The lady said her husband had been meaning to "take it apart" to fix it.
Do you know anything about this Polaris 380 in terms of how it works?
What would you look for when it's not moving or gathering debris?

I'm a noob in terms of the fact that I've never had a pool cleaner before.
Any suggestions for how to test it given I don't have a booster pump (nor a vacuum pump).

All I have is this 1.6HP portable submersible sump pump with a 1.5 NPT which gushes out water at 80 gallons per minute.
Which should be enough volume, right?

The lady said it probably doesn't work - and she's likely right.
What would you do first to debug?

 

[ajw22]

Polaris Pool Cleaners - Further Reading

www.troublefreepool.com

 

[Dirk]

I have a suction side cleaner. It came with a flow gauge to determine and set the proper flow for the cleaner. That got me thinking that there must be something similar for a pressure-side cleaner, and there is. It's covered in the article Allen linked for you. Until you can establish proper pressure flow to your cleaner, all your other troubleshooting and/or repair efforts will be tough going if not impossible. You're looking for a Polaris Pressure Stick.

I don't know much about pumps, and way less about the 380, but I'm thinkin' a sump pump is not going to give you the correct flow and pressure to run that cleaner, which means you might have to get yourself an actual booster pump, which could be a case of throwing good money after bad. How much are you willing to gamble to bring a used, broken cleaner back to life?

Does your pool even have the plumbing and port to support a pressure-side cleaner?

Don't mind me. I hated my Polaris 280 and its delapidated booster pump. It was a happy day when I got rid of both. So I'm projecting some. Others here swear by theirs, so whaddaIknow... I like robots even less (though I've never owned one), but in this case I might recommend putting money towards one of those before trying to get a pressure-side cleaner to work if you don't have a pressure port in your pool.

 

[Bperry]

Does anyone here have practical experience with the Polaris 380 pressure-side pool cleaner?

At a garage sale I picked up this Polaris 380 pressure-side pool cleaner. Lady who sold it said her late husband used it but it was probably broken.
And it is. It doesn't seem to have any missing parts from the outside (and she gave me a box of additional parts); but it's not moving or suctioning up when I put a 1.6HP 5000gph sump pump on the pressure side.

The lady said her husband had been meaning to "take it apart" to fix it.
Do you know anything about this Polaris 380 in terms of how it works?
What would you look for when it's not moving or gathering debris?

I'm a noob in terms of the fact that I've never had a pool cleaner before.
Any suggestions for how to test it given I don't have a booster pump (nor a vacuum pump).

All I have is this 1.6HP portable submersible sump pump with a 1.5 NPT which gushes out water at 80 gallons per minute.
Which should be enough volume, right?

The lady said it probably doesn't work - and she's likely right.
What would you do first to debug?

Those are very sensitive to dirt getting in the line and clogging the jets inside the drive box. You can try taking it apart and blowing air through the jets. It works like a small water powered windmill. It’s very simple but even a grain of sand can clog it.

 

[ajw22]

Proper pressure can be determined by wheel RPM as described in the Installation Manual.

 

[Dirk]

Proper pressure can be determined by wheel RPM as described in the Installation Manual.

Yes, unless it won't roll at all. @ajw22, is there a way he can check the pressure without it being able to roll? Will a Polaris Pressure Stick be accurate if the vac head is broken, or just clogged up? Or is it a kind of a chicken-egg dealio? He can't tell if his repair efforts are working without the proper pressure, and he can't test for the proper pressure without the vac working?

 

[Gary Davis]

Since I'm a noob to pool cleaners and booster pumps, I appreciate the kind TFP cleaner reference from Allen and the TFP booster pump thread for beginner starting points.
To clarify by answering the kind questions asked of me...

I have a suction side cleaner. It came with a flow gauge to determine and set the proper flow for the cleaner.

I have tried the suction-based hand-held pole-mounted heavy roller vacuum attachments, which work, but priming the 60-foot hose is not only a two-man job but any mistake runs the main filter pump dry.

That got me thinking that there must be something similar for a pressure-side cleaner, and there is.

Up until yesterday I had thought all the pool cleaners were based on vacuum (which I can get out of the debris canister but it's way too much work and requires two people to prime the hoses).
On my supposedly "self cleaning" pool, there is no dedicated vacuum port, nor is there a dedicated booster output port (as, I guess, they weren't deemed to be needed).

As a separate project, I plan on retrofitting the 1.6HP sump pump to reverse the flow as a vacuum pump instead - but that's for later as this pressure-side Polaris 380 pool cleaner fell into my lap.

It's covered in the article Allen linked for you. Until you can establish proper pressure flow to your cleaner, all your other troubleshooting and/or repair efforts will be tough going if not impossible. You're looking for a Polaris Pressure Stick.

Thanks for the "Pressure Stick" keyword, which I found mention of in this POLARIS 380 REPAIR MANUAL (which seems to be a workbook for some kind of training class).

I don't know much about pumps, and way less about the 380, but I'm thinkin' a sump pump is not going to give you the correct flow and pressure to run that cleaner, which means you might have to get yourself an actual booster pump, which could be a case of throwing good money after bad. How much are you willing to gamble to bring a used, broken cleaner back to life?

I certainly know less than anyone does about pool cleaner where the likely answer to your question, as you clearly surmised, is perhaps that it's probably not worth buying a booster pump just to test (and fix) the Polaris 380 that fell in my lap.

However. It may be worth utilizing the existing brand-new 1.6HP 5500GPH (~90 gallons per minute) submersible sump pump to act as an (unfiltered) booster pump.
Perhaps I can sit the sump pump on a ledge over the deep end and maybe let the pool cleaner do its thing in the deep end (which is where all the debris collects over time).

Does your pool even have the plumbing and port to support a pressure-side cleaner?

It's a long story that will bore you to death, so the short answer is "no".
That's why any working solution has to be a portable setup (plugged into a 120VAC GCFI on the pool deck).

Don't mind me. I hated my Polaris 280 and its dilapidated booster pump. It was a happy day when I got rid of both. So I'm projecting some. Others here swear by theirs, so whaddaIknow...

I assume these pressure-side pool cleaners must work, albeit I'm sure they break down a lot.
Since I already have the 1.6HP 90gpm submersible sump pump with a perfect 1.5-inch NPT output (which I bought to empty the pool a month ago), I'm hoping my setup may be virtually free to get this Polaris 380 pressure-side cleaner working.

1. My first problem to resolve, I think, is that the sump pump is too powerful.
   • The question to answer would be either how to reduce the output, or, if the Polaris 380 can handle that much higher output
2. Concurrently, I have to figure out what's wrong with the Polaris 380 in the first place
   • Where without a booster pump, I can't really test it (as far as what I know at the moment)

But I still have a lot of basics to learn. For example, I haven't yet figured out if these pressure-side cleaners are FILTERED (i.e., are they supposed to go through the main filter?).
Or is all the debris and detritus collected in the filter bag (as the garden-hose hand-held pole cleaners do).

Mine won't be filtered unless I add a separate topside filter to it, so that's an important question to iron out (which I would have known if I had any experience with pool cleaners).

I like robots even less (though I've never owned one), but in this case I might recommend putting money towards one of those before trying to get a pressure-side cleaner to work if you don't have a pressure port in your pool.

I am on fixed income and don't have the money for fancy pool equipment.
I have all the time in the world - and no money. So my solution will take that into account.

Looking at the link Alan kindly provided and the TFP booster pump link and a few other TFP repair handbooks & troubleshooters, I think my main goal is three fold initially:

1. First I need to figure out how the Polaris 380 system is SUPPOSED to work (e.g., is a filter required?)
2. Then I need to drop down the 1.6HP 90gpm 1-1/2-inch NPT sump pump output closer to what the 3/4HP ~12gpm 1-inch NPT booster pumps typically output (e.g., 50psi).
3. And, once I have the lowered sump pump output (of about 28psi), then I have to figure out what's wrong with the Polaris 380 cleaner I picked up at the garage sale yesterday.

Notice I don't have a pressure gauge yet, so I only know the sump pump is 5500 gallons per hour output (92GPM) while the Polaris 380 needs 28psi to 32psi at the robot, where I see from the TFP booster pump thread that some of the booster pumps output about 50psi at about 12GPM to 13GPM (so I need to add a hefty resistance, I think, where suggestions are welcome).

 

[Mdragger88]

A pressure side cleaner only collects debris in its bag or basket (in this case- bag). Since it works on the pressure (return) side of the pump by default it cannot move debris into the system’s filter.
Here’s a good parts list & diagram

Polaris 380 - Head Parts - INYOPools.com

Polaris 380 - Head - INYOpools.com has the largest selection of swimming pool and spa replacement parts with over 70,000 parts in stock. Order today and save!

www.inyopools.com

 

[ajw22]

Yes, unless it won't roll at all. @ajw22, is there a way he can check the pressure without it being able to roll?

The Installation Manual says to put the cleaner on its side to measure wheel RPM. It does not need to move. The wheels should be free spinning.

If the wheels do not turn when on its side then there are problems with the internal mechanism and not water pressure.

 

[Dirk]

OK, I'm following you, especially about the budget. No port. Must me a stand-alone. Got it.

You gotta figure out the pressure first, I think. If the Polaris wheels don't move as Allen suggests, then either the vac is not working, or the pressure is not adequate. I suspect both. Keep in mind, the pressure should be within a range: both too low and too high is no good. Also note that a booster pump typically takes its water from AFTER the pool's main filter, so that it's nice and clean. If you're drawing water directly from the pool with your sump, it'll likely draw in some crud at some point and fowl your newly-fixed vac, if you ever do get it running. So you have to solve for that, too.

Can you spring for the Pressure Stick and required pressure gauge? I can't imagine proceeding with the vac repair without knowing the pressure is right. Or you could try taking the whole thing apart to see if there is something obvious, before you buy anything else. Broken gears? Clogged jets? Etc. (Just guessing, I've never worked on one.)

The reason I didn't like my 280 was because of the tail. I could just never get it working right, and it would spray my yard, my windows, me! It knew I hated it, and retaliated every chance it got!!

Sidebar, priming a suction vac hose is not a two-man job (or shouldn't be). If you'd like to explore ways to prime it yourself, we can help you with that.

 

[Dirk]

My first problem to resolve, I think, is that the sump pump is too powerful.

Again, I'm no expert on these vacs, just brainstormin' with ya. If the pump is too powerful, that should be an easy/cheap fix. You could rig up a splitter, and send half the water to the vac, and the other half back to the pool. Adjusting the flow of each should dial in the pressure to the vac, without putting too much back-pressure on the pump. But, as I mentioned, you still need to figure out the pressure on the line going to the vac. Something as simple as this guy might work to regulate the pressure to the vac, just a few bucks at Lowes:

One side to the vac, the other to a short hose that goes into the pool. You'd want to use that short hose, as opposed to spraying the surface of the pool directly from the splitter. That spray will create havoc with your pH. Better to return the excess water to well below the surface. You'd open up both sides full, then dial down the side to the vac until you get the right pressure to the vac. Leave the other side open wide, unless you can't get enough pressure to the vac, at which point you'd dial down the other side until you do (leaving the vac side wide open). Just a matter of balancing this simple bypass setup to get the pressure you need.

But ya also gotta get some sort of filter on the sump's intake, or else you'll just clog up the vac. You'd need to solve the filter first, because depending on what you use, that will probably affect the pressure of the output.

 

[1poolman1]

Does anyone here have practical experience with the Polaris 380 pressure-side pool cleaner?

At a garage sale I picked up this Polaris 380 pressure-side pool cleaner. Lady who sold it said her late husband used it but it was probably broken.
And it is. It doesn't seem to have any missing parts from the outside (and she gave me a box of additional parts); but it's not moving or suctioning up when I put a 1.6HP 5000gph sump pump on the pressure side.

The lady said her husband had been meaning to "take it apart" to fix it.
Do you know anything about this Polaris 380 in terms of how it works?
What would you look for when it's not moving or gathering debris?

I'm a noob in terms of the fact that I've never had a pool cleaner before.
Any suggestions for how to test it given I don't have a booster pump (nor a vacuum pump).

All I have is this 1.6HP portable submersible sump pump with a 1.5 NPT which gushes out water at 80 gallons per minute.
Which should be enough volume, right?

The lady said it probably doesn't work - and she's likely right.
What would you do first to debug?

Very seldom, as in I've never seen it work, will a pump other than a true booster pump like the Polaris PB4-60 or the many others like it, make a Polaris, or any other pressure-side cleaner, work properly.

 

[Gary Davis]

He can't tell if his repair efforts are working without the proper pressure, and he can't test for the proper pressure without the vac working?

Thanks everyone for the kind advice as I am a complete noob when it comes to pool cleaners.

You said that right where I think I probably have too much pressure/volume (nominally at 90 gallons per minute instead of about 12 or 13 gallons per minute) but I do need to invest in the proper pressure testing apparatus, as I can always LOWER pressure (e.g., with the suggested diverter valve).

The Installation Manual says to put the cleaner on its side to measure wheel RPM. It does not need to move. The wheels should be free spinning.

If the wheels do not turn when on its side then there are problems with the internal mechanism and not water pressure.

A pressure side cleaner only collects debris in its bag or basket (in this case- bag).

Ah! Perfect. When I hold it up in the air & run the sump pump, I see water spritzing out of the case bag, so I can presume, for now, that the suction part "might" be working.

Since it works on the pressure (return) side of the pump by default it cannot move debris into the system’s filter.

Thanks for confirming the debris is collected in the bag and the rest of the water goes back into the pool, unfiltered.
I can see a few places where, when held in the air, the water sprays out of various openings.

Here’s a good parts list & diagram

Polaris 380 - Head Parts - INYOPools.com

Polaris 380 - Head - INYOpools.com has the largest selection of swimming pool and spa replacement parts with over 70,000 parts in stock. Order today and save!

www.inyopools.com

Thanks for that parts list, as the wheels aren't spinning when I hold it up in the air; so I'm assuming that's the first thing I need to look at to see why they're not moving.
Do all three wheels drive or is it like a 2WD conventional vehicle with a differential where only one wheel is doing the traction at any given time?

 

[Gary Davis]

The Installation Manual says to put the cleaner on its side to measure wheel RPM. It does not need to move. The wheels should be free spinning.
If the wheels do not turn when on its side then there are problems with the internal mechanism and not water pressure.

Thanks for that advice as I'm still trying to figure out how this garage-sale Polaris 380 cleaner works.
To be sure, none of the wheels are turning when I drop the sump pump into the pool and hold the cleaner in the air - so I think the wheels turning may be where I need to explore first.

OK, I'm following you, especially about the budget. No port. Must me a stand-alone. Got it.

The boring part is that the pool has three pumps, one for the spa jets alone, and another for the skimmers which are unfiltered. The water goes from the two skimmers into the skimmer pump and then back into the pool after traveling through the space ship that has a million plastic gears that control the 20 or so popups in sequence. These popups spray unfiltered water from the skimmers back into the pool (where the only "filter" is the skimmer basket and the skimmer pump basket).

While everyone with a normal pool says you can vacuum using the skimmer port (one is blocked off so there is only one port), there isn't much vacuum to speak of - certainly not enough to run a pool vacuum.

On the other hand, the main drain has vacuum that will suck your arm out of its socket. The main pump sucks water from the bottom of the spa and from the bottom of the deep end. From the deep end it goes into the topside debris canister (which catches large debris like leaves and sticks) and then from there to the filter pump and then to the filter and back to the return ports. This is where tremendous vacuum can be obtained, but it's difficult because you have to stick your hand a couple of feet down into the debris canister hole to shove the 1-1/2 inch vacuum hose onto the port (which isn't designed for this so there are no threads). Then you have suction. Tremendous suction, in fact.

But you have to prime the two 30-feet vacuum hoses in the pool at the same time that you're shoving your arm two feet into the debris canister to get the suction to hold it in place.
I don't see how it's even possible to do with a single person, but I guess if you prime the hose first in the pool and then really quickly jump out of the pool before the water drains to shove it shoulder deep into the debris canister, you might make the connection in time - but what if the main pump runs dry? Is it worth it just to get vacuum?

You gotta figure out the pressure first, I think. If the Polaris wheels don't move as Allen suggests, then either the vac is not working, or the pressure is not adequate. I suspect both. Keep in mind, the pressure should be within a range: both too low and too high is no good.

Given how powerful the sump pump is, I suspect the pressure is too high; but luckily, flow can be diverted as was suggested in this thread.

Also note that a booster pump typically takes its water from AFTER the pool's main filter, so that it's nice and clean. If you're drawing water directly from the pool with your sump, it'll likely draw in some crud at some point and fowl your newly-fixed vac, if you ever do get it running. So you have to solve for that, too.

Thank you for bringing that up, as I'm currently testing with the sump pump on a high ledge which could collect debris. I think I can maybe solve that problem by putting the sump pump in a bucket with holes in the bucket and a cloth sleeve around the outside of that bucket - but I'll worry about that later once I have the pool cleaner actually working.

Can you spring for the Pressure Stick and required pressure gauge? I can't imagine proceeding with the vac repair without knowing the pressure is right. Or you could try taking the whole thing apart to see if there is something obvious, before you buy anything else. Broken gears? Clogged jets? Etc. (Just guessing, I've never worked on one.)

I definitely plan on taking it apart. The lady said her husband used to take it apart all the time and when he put it back together, that would fix it.
She wasn't sure what he was doing, but the assumption here is that a piece of crud may have fouled the transit mechanism perhaps.

The reason I didn't like my 280 was because of the tail. I could just never get it working right, and it would spray my yard, my windows, me! It knew I hated it, and retaliated every chance it got!!

I just noticed this thing also has a foam-covered tail that spritzes out water. I guess it's to stir up the debris?

Sidebar, priming a suction vac hose is not a two-man job (or shouldn't be). If you'd like to explore ways to prime it yourself, we can help you with that.

If you've used the suction from a topside debris canister, I'm all ears for how to do it alone as there are no threads. Just a hole that is about two feet below the deck (at least). So you are lying on your side with one arm almost completely in the debris canister hole shoving the hose into the hole... but wait... you have to run to turn the main pump on... but wait... you can't let it run dry... so you have to have already primed the two 30-foot connected lengths of 1-1/2 inch vacuum hose - which is primed in the pool... so... you jump out of the pool, shove your entire arm into the canister hole and then turn on the pump.

I used to do it with three people but it can be done with two people if you are really fast about disassembling the canister (which is partly why it broke). Personally, I'd say it's impossible to do alone, but maybe there are a few tricks that allow it to be done alone without risking running the main pump dry for too long.

 

[Gary Davis]

Again, I'm no expert on these vacs, just brainstormin' with ya. If the pump is too powerful, that should be an easy/cheap fix. You could rig up a splitter, and send half the water to the vac, and the other half back to the pool. Adjusting the flow of each should dial in the pressure to the vac, without putting too much back-pressure on the pump. But, as I mentioned, you still need to figure out the pressure on the line going to the vac. Something as simple as this guy might work to regulate the pressure to the vac, just a few bucks at Lowes:

Thanks for that diverter-valve idea to lessen the 90 gallons per minute of the 1.5HP sump pump to closer to the 12 gpm to 13 gpm that a proper 3/4HP booster pump would have provided.

While I know nothing about pool cleaners, I'm a veritable expert at garden hoses and their related brass fittings, so I have a ton of those diverter valves, which, although they're garden hose threads, can be retrofitted into NPT with the proper adapters. [Note to self: Create a thread on garden-hose fittings as I'm a self-taught expert on what works and what doesn't work.]

One side to the vac, the other to a short hose that goes into the pool. You'd want to use that short hose, as opposed to spraying the surface of the pool directly from the splitter. That spray will create havoc with your pH.

Agreed. As you noted, I have high alkalinity (even after cases of muriatic acid), so the last thing I want to do is aerate the pool, which will bubble off the carbonic acid CO2 and cause the pH to rise.

Better to return the excess water to well below the surface. You'd open up both sides full, then dial down the side to the vac until you get the right pressure to the vac. Leave the other side open wide, unless you can't get enough pressure to the vac, at which point you'd dial down the other side until you do (leaving the vac side wide open). Just a matter of balancing this simple bypass setup to get the pressure you need.

I like this idea, where I can dial in the pressure using the diverter valve, and pump the excess water into the far reaches of the pool.
Since a sump pump is 1.6HP and 90 gallons per minute, it should be possible to divert enough water to output 28 psi at about 12 gallons per minute.

But ya also gotta get some sort of filter on the sump's intake, or else you'll just clog up the vac. You'd need to solve the filter first, because depending on what you use, that will probably affect the pressure of the output.

While the ledge above the deep end looks pretty clean, I think I'll solve that problem by drilling holes in a bucket and placing the sump pump into that bucket and covering the outside of the bucket with a sheath of cloth. I think that will keep the debris out - but first I have to get the cleaner's wheels to spin.

 

[Gary Davis]

Very seldom, as in I've never seen it work, will a pump other than a true booster pump like the Polaris PB4-60 or the many others like it, make a Polaris, or any other pressure-side cleaner, work properly.

Thanks for that advice. I never heard of a booster pump until yesterday (as I always thought these cleaners ran off of vacuum), so I was already in the middle of my task of turning the sump pump into a vacuum pump by adding this 1.5-inch NPT opening to the bottom of the sump pump (and blocking off all unnecessary openings other than the 1.5-inch NPT port).

But now that I have a PRESSURE-SIDE robotic cleaner, if I can get it to work, I likely won't need those manual on-a-stick vacuum attachments (I hope).


Given a bona-fide booster pump is only about 12GPM to 13GPM at about 50PSI (based on the specs quoted previously), it seems to me that I have way more than that, so my problem will mostly be the following two independent tasks:

1. First, I need to figure out what's wrong with the Polaris 380 wheel mechanism,
2. And then, I'll worry about diverting the 1.6HP 90GPM water flow down to less than 12GPM at about 50PSI (or so).

 

[Bperry]

Thanks for that advice. I never heard of a booster pump until yesterday (as I always thought these cleaners ran off of vacuum), so I was already in the middle of my task of turning the sump pump into a vacuum pump by adding this 1.5-inch NPT opening to the bottom of the sump pump (and blocking off all unnecessary openings other than the 1.5-inch NPT port).

But now that I have a PRESSURE-SIDE robotic cleaner, if I can get it to work, I likely won't need those manual on-a-stick vacuum attachments (I hope).
View attachment 607340

Given a bona-fide booster pump is only about 12GPM to 13GPM at about 50PSI (based on the specs quoted previously), it seems to me that I have way more than that, so my problem will mostly be the following two independent tasks:

1. First, I need to figure out what's wrong with the Polaris 380 wheel mechanism,
2. And then, I'll worry about diverting the 1.6HP 90GPM water flow down to less than 12GPM at about 50PSI (or so).

Open up the motor box and find out

 

[Dirk]

I don't see how it's even possible to do with a single person, but I guess if you prime the hose first in the pool and then really quickly jump out of the pool before the water drains to shove it shoulder deep into the debris canister, you might make the connection in time - but what if the main pump runs dry? Is it worth it just to get vacuum?

You don't have to be in the pool. Connect the hose to the vac head and the vac head to the pole. Push the vac head, with the pole, down into the deep end. Now some of the hose is in the pool, the rest is lying on the deck. The hose section in the water will be full of water. The hose section on the deck should be near your skimmer. Kneel next to the skimmer, grab the hose a few inches above where it enters the water, and slowly feed that chunk of hose into the water, repeat, repeat, repeat, a foot or so at a time. As long as the "dry end" is out of the water, and you continue to feed the hose into the water as described, the hose will fill with water and the air will escape out of the dry end. Continue feeding until the dry end goes underwater, and keep it under water. It doesn't matter if some or most of the hose is floating on the surface. If you fed it down into the water correctly, it'll all still be 100% full of water. Now feed the end of the hose through the skimmer mouth and into the skimmer well, keeping it under water the whole time. Then connect the end to the suction port at the bottom of the well. Again, even if the hose is mostly floating, that's just the plastic floating, there won't be any air in it. Then turn on your pump. One man job.

If you can't get the hose to feed through the skimmer opening, that's OK. While the end is underwater in the pool, seal it with your palm. Lift it out of the water and plunge it quickly into the opening to the skimmer well. You might get a gulp of air if you don't do it perfectly, but the pump can handle that. Then connect the end to the suction port at the bottom of the skimmer. Then turn on your pump. Still a one man job.

 

[Dirk]

... I think I probably have too much pressure/volume (nominally at 90 gallons per minute instead of about 12 or 13 gallons per minute)

You're thinking of that wrong. Forget gallons per minute. That's volume, or flow rate. That's not what drives the vac. The pressure does. You can move 90 gallons of water very quickly with low pressure (think of a bathtub draining through a very large drain). And you can pump very little water at high pressure (think of a power washer). Flow and pressure are two different things. You keep referring to them interchangeably. If anything, they are the inverse of each other. Typically, a sump pump is rated using gallons per minute at virtually no resistance (like with nothing connected to it). Connect a hose, and the volume drops. Try to pump uphill, with the same hose, and the volume plummets. Put a sump in the bottom of a pool and try to pump it up and out and all the way to the street, and even a 90GPM sump will take forever. You don't get 90GPM no matter what, what's connected to the pump (before it and after it) govern the actual GPM flow.

Once you connect your sump to your vac, the volume, the flow rate, takes a dump. If the pump's impeller is designed for large flow, it probably cannot generate much pressure. Different pumps have different characteristics. Some move a lot of water, some generate a lot of pressure. Some can't do either well, some can do both really well. As @1poolman1 points out, your sump probably (likely) doesn't have the characteristics to feed the vac like a true booster pump does. It's probably designed for large flow, not high pressure.

but I do need to invest in the proper pressure testing apparatus, as I can always LOWER pressure (e.g., with the suggested diverter valve).

Yes, you do need the tester. Once you get the pressure testing apparatus, you'll know: If the pump can't achieve the required PSI through the tester, then you're done. You can quit while you're ahead, unless you want to spring for a booster pump. If you're sure you won't be buying a booster, you should check the pressure first, before spending time and money fixing a vac that you'll never be able to use.

 

[Dirk]

I just noticed this thing also has a foam-covered tail that spritzes out water. I guess it's to stir up the debris?

Yes, a pressure vac cleans in two ways. It sucks bigger stuff off the bottom into its onboard bag. And its tail swishes around to suspend the fine silt that has settled on the bottom into the water column, where it can get sucked into the skimmer. Though in your pool's case, that won't be very productive, since you say your skimmers don't lead to a filter.