Troubleshooting low flow, low psi, help!

[Hands]

First post on this awesome forum, I've poked around, lurked around a bit, superb stuff here, thanks to all!

My problem is that my suction is too weak to properly run my new 4 wheel PoolCleaner on the low speed of my 2 year old two speed pump. And I cannot understand why.

By my approximate calculations of head and the pump curves from the manual, I should be getting 32 GPM. I plugged my numbers into Mas985's awesome pump tools spreadsheet and get 28 GPM. But I just don't see it in practice. Or more accurately, I only get 6 rpms on the PoolCleaner wheels where it requires 12 rpm. I've read that this particular cleaner works with even 15 GPM. So I am missing something.

I first thought that I had a suction side leak, as there was air in the basket when the suction cleaner was attached. But after smoke test, shaving cream test and replacing Orings, I realized I was not completely eliminating the air from the hose, because doing so eliminates the air. So now I am thinking its a clog. But hose and shop vac have not dislodged anything. Impeller feels clean and looks clean when inspected with one of those tiny cameras.

One thing I cannot understand is when the pump is on low speed, I can completely close off the suction line (with a plug), and it still does not cause any air in the pump basket. Initially, I thought this confirmed that I did not have a suction air leak but now I am not sure. Shouldn't the basket evacuate?

1. At low speed gauge reads 2 psi, goes to 12 psi on high speed.
2. On high speed no air in basket. If I prime with high speed and switch to low speed then no air or very little air in the basket.
3. On high speed with suction cleaner attached, a lot of air in the basket.

Thank you for your time and sorry this is so long!

 

[dpost94]

What type of filter do you have? Have you considered cleaning it or changing the media? Additionally, have you changed the pump lid o-ring? More often than not the bubbles in the pump are because of that o-ring. Even if it looks in good shape it should be snug. It may be stretched out a little and hard to tell.


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[Hands]

Sorry DPost94, I should have mentioned that. I thought my signature would show but it doesn't seem to be showing. Its a Hayward Sand Filter. Sand is about 2 years old, backwashing is done every two weeks. O ring was also changed this past week and lubed.

The sand filter seems to be doing its job. Pool water is clear.

 

[Texas Splash]

Hello Hands and welcome to TFP! Also welcome to Dpost94 as I believe this was your first post as well.

Hands, a low flow/elevated psi could be a couple things. The one basic thing I'd like to rule-out right away is chemistry. If you've spent any amount of time on the site you know how much we value proper water testing as often times excessive organics slow-down water flow and increase psi without being noticeable to the naked eye. Can you post a full set of test results from your TF-100 or Taylor K-2006 test kit? That would help a lot and at least help us rule-out some basic chemistry. Thanks, and great to have you with us.

 

[dpost94]

Have you checked your cleaner hose for holes? If you get air in the pump with the cleaner on then I would check that.


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[Jimrahbe]

Hands,

It appears to me things are working like they should...

I doubt your cleaner will every work on your low speed. With a filter PSI of 2, my guess would be that your pump is running at 1,500 RPM...

I think at that speed you will get some air under the pump lid.

Things work at full speed, 12 PSI sounds like you filter is not clogged and working great...

But... I've been wrong about at thousand times before,... and that was just today...

Thanks for posting,

Jim R.

 

[Hands]

Thanks dpost94 and Texas. The cleaner hose is brand new, I've held sections of it out of the water and not heard any hissing. I'll blow out all the air and check it again this evening, bicycle tire style. Just to double check.

I think its unlikely that chemistry is a problem. The pool water has just been replaced 1 month ago, all the tests from my basic Poolmaster test kit are in the ideal range. Ph, Cl, TA. CYA = 40 from pool store computes with the number of tablets I have added. I'm surprised that invisible organics can affect water flow, but you learn something new everyday! I'd guess that if it was small enough to be invisible (say less than 100um), it would not bother the filter. Still, I don't think that is my problem because I have backwashed thoroughly and not seen any improvement.

Edit: I also tried this in recirculate mode which bypasses my filter and did not see any improvement. Unless, the invisible organics are somehow affecting the viscosity of the water, I cannot see how they can affect water flow or affect psi.

 

[Hands]

Ha ha! Thanks Jim! Ugh, so you are saying it just might not have enough juice to run at low speed, thats a bummer. Nothing I can adjust? I can't switch off any of the returns as they are all grouped.

I have a good 70 ft of 1.5 inch pipe on the return side. The two speed pump runs at 1725 rpm.

I am wondering if someone who has a PoolCleaner working at low flow rates that is supposedly famous for can chime in. The PoolCleaner does move, just misses spots, does not climb walls and hardly goes into the shallow end.

 

[dpost94]

Couldn't you just put a plug in one of your returns?

 

[Jimrahbe]

Hands,

I have a robot so I'm no expert here, but if you don't use the high speed for the cleaner, what do you use it for???

I "assume" that when running at high speed the cleaner works fine? If so why not have the cleaner run at high speed and use low speed for everything else?

Your cleaner is a "suction" cleaner, right?? How do you connect it to your pool?

Thanks,

Jim R.

 

[Hands]

Hmmm, I didnt think of that dpost94. My impression was that blocking a return at its exit would not help because the pump would still be pushing water right up to there. But maybe, thats not true because it is "dynamic head". Let me try that tomorrow. Though, I am loathe to switch of any returns permanently as I think I need all the circulation I can get. Also, I double-checked the hose, there is no leak.

At this point, I just want to know if everything is performing according to spec and the flow is just what it is for the system.

Jim, thanks. If I cannot sort this out I am going with a robot too. Seems much less hassle, the only thing holding me back was I didn't want to pull it out after every cleaning. Do you leave yours in all the time? I use the high speed for backwashing. According, to the numbers on Mas985's spreadsheet, its 1319W at high speed and 319W at low speed for my setup. Cleaner running 3-4 hours a day. That quickly becomes expensive. The suction cleaner plugs into the skimmer port.

 

[dpost94]

Or could you just plug the return when your are using the cleaner?

 

[Hands]

I'm going to try it tomorrow, might have to get some easy to switch of return fixture.

I'm not sure it will work because as I was thinking about it, if we consider the limiting case of closing all the returns there will be no flow. But this stuff is counter-intuitive sometimes, it might depend on the friction that the flowing water experiences. Nothing like an experiment to sort it out! Thanks for helping out dpost94

 

[kadavis]

How do you have the cleaner installed, do you have a dedicated line or our you using the skimmer. Are you using the flow regulator valve . You should probably set the cleaner to run when on high speed for a couple hours a day then run pump on low for the rest of your filter cycle

 

[Hands]

Thanks kadavis, I have the cleaner plugged into the skimmer. I use a poolskim on one of the returns to do the skimming. I am trying to get this to work on the low speed. If it won't work then I will give up and go robotic.

Where I am stuck is that by all my calculations (attached) and by my pump head curves, this should work with low speed. The cleaner is reported to work at 15 GPM, I should have between 25-30 GPM. So I trying to figure why that is not happening and what I am missing.

 

[Sfpat]

Have you closed up others avenues of suction to the pump, such as bottom drain, other skimmers, ect? Start with only the skimmer that the cleaner is attached to being opened. Then open others a bit if the draw through the cleaner is too strong.

 

[Sfpat]

Any chance you have a partial plug in the pump suction line (leaves, etc) which is normally the cause of air leakage into my pump (pre TFP days)? I used to travel a lot and my pool boys (sons) didn't always give the pool the attention it needed. To clear the line, I use a plumbing bladder attached to a hose. Open the pump lid, insert the bladder into the suction line and flow backwards to the skimmer, with all other suction valves closed. I have a 6 foot pvc pipe that I screw into the skimmer that has a valve on the other end. I then pulsate the line (close valve for 10-15 seconds then open quickly). I've been amazed at the amount of "junk" that comes flying out (just be prepared to get rained on). Usually 5-10 pulses will get everything out and the air bubble issue goes away. Now that my travel has been substantially reduced, it's been several years since I have had to do this.

 

[mas985]

View attachment 60804

Thanks kadavis, I have the cleaner plugged into the skimmer. I use a poolskim on one of the returns to do the skimming. I am trying to get this to work on the low speed. If it won't work then I will give up and go robotic.

Where I am stuck is that by all my calculations (attached) and by my pump head curves, this should work with low speed. The cleaner is reported to work at 15 GPM, I should have between 25-30 GPM. So I trying to figure why that is not happening and what I am missing.

Did you do this calibration at full speed with the cleaner attached? Also, is ALL the flow going through the cleaner line and is none being bypassed. The problem is that you probably will not be able to calibrate the model with just flow going through the cleaner and the pump at high speed because the pump will likely draw air and lose prime because the suction head will be so high.

But if you have the lines configured for 100% of the flow going through the cleaner and the pump on low speed and the RPM is less than 10, then it probably won't work. I had the same problem with my pump on low speed with that cleaner. When you redirect all the flow through the cleaner, head loss goes up and flow rate goes down so the RPMs go down as well. You would probably need a much larger pump to get it work well on low speed.

 

[Hands]

Wow! Hi Mas985, thanks for helping out. Awesome work you do here. Calibration was done at full speed WITHOUT cleaner attached. All the flow is going to skimmer. I have a simple set-up. Old pool. The main drain plumbs to the single skimmer (I have that closed off), and the skimmer goes straight into the pump, no valves. no heater, no solar. nothing really adjustable.

I was hoping I could pick your brain on two fronts:
1. Measuring my return lines and guessing at the fittings, I get a return equivalent length of 135 Ft of 1.5 pipe, Suction equivalent length is 42 ft of 1.5 pipe.
On the return side, at 60 GPM, that translates into 27 ft of head, Adding 3 Ft for the sand filter (I read that is a good enough approximation), I get at an experimentally estimated 30 Ft of head for the return side. The Pump Spreadsheet calculates at 39.4 ft. Could the difference be evidence of a blockage? I haven't tried the drain king but a hose and shop vac have not helped.

2. One thing I cannot understand is when the pump is on low speed, I can completely close off the suction line (with a plug in the skimmer), and it does not cause any air in the pump basket. Initially, I thought this confirmed that I did not have a suction air leak but now I am not sure. Shouldn't the basket evacuate?

 

[jimingreen]

I had a similar problem when I opened my pool a couple years ago. I was beating my head against the wall looking for a suction side leak or a blockage. It turned out to be a tear in one of the internal gaskets in the pump. The impeller could not develop pressure because of the tear. I bought a gasket kit and made it like new. Was a simple fix.