New pump, low flow....

[Merccooper]

I'm sorry to be constantly asking questions, but I can't seem to catch a break.
Now that the suction leak has mysteriously disappeared (I guess that is a break!), I started to vacuum for the first time this season only to find the flow is almost too low to even keep the vacuum hose suctioned to the skimmer. I thought maybe the vacuum hose was plugged, but when I checked out the skimmer and the returns I noticed there was no where near as much flow as with the old pump. I'm hoping that something is stuck somewhere in the line and that I didn't buy too small of a pump.
- My old pump was a Hayward 1hp (not sure of the model)
- New pump is a Hayward Max Flow VS 1.5 hp.
- The pump is 45 feet from the skimmer (60 feet from drain) and about 2 feet below the surface.
- 1.5 inch pipe
- I have about 5 90 degree turns (plus the SWG, heater, filter)
- I was running at 3000 rpm
- Filter has max working pressure of 50 PSI.
- The flow rate on the filter says "Flow rate US gpm/soft" = 15 for filter pump 7lvl and 7MAG-U or 20 for filter pump 1lvl and 1MAG-U
- The flow is low when coming either from the drain or the skimmer.
- It "appears" to have great flow when backwashing

 

[Melt In The Sun]

What is your filter pressure with the pump running? It will be low if there's somthing stuck in the suction line. That pump is certainly adequate!

 

[Merccooper]

It 17 PSI.

I was hoping to hear a similar comment as you made My wife would have killed me if I didn't get a strong enough pump!

I guess I begin the search for something stuck...but I wouldn't think it is stuck in the suction line since both the drain and skimmer have the same problem. My thought would that the pressure would be much higher if the problem was after the pump.
.

 

[Melt In The Sun]

Yep, you're right, it would be high. 17 is awfully low for running at 3000 rpm...i think you've got something stuck in there. Is the strainer basket and impeller clean? I'd start there...

 

[Merccooper]

Yup, basket is empty. I would assume the impeller is clean as well since it is a new pump and only run really for the last two days.
Tomorrow I'll have to do some more inspections.....getting tired of the fight though.

 

[Merccooper]

I'm continuing my investigation of this. In an attempt to narrow things down, I've opened up an existing spice near the pool edge of the return line to see what the flow was like. I was able to measure the flow at about 45 GPM...which is what (one of the) specifications indicates for 1.5 inch piping. So, at least to the pool edge, it looks like I'm getting the expected flow (more on this below). PSI at this point is 15.

To compare this, I measured the flow to backwash. The flow was just a little too much for the bucket I was filling (it would splash out rather than fill), so the flow rate was higher. PSI at this point is 12.

So now, I'm trying to compare the specifications of the old pump (Hayward Super Pump 1hp SP2607X10) to the new pump (Hayward Max flo 1.5hp VS SP2300VSP). This is where I'm having troubles comparing apples to apples and wouldn't mind some help.

The first image is for the old pump. If I read it correctly, it says I should get about 50 GPM with 40 head feet.
The second image is one version of specifications for the new pump. If I read it correctly, this says I could get 75 GPM at 3000 rpm with 40 head feet, but I assume this is with 2" piping.
So, looking at the third image (another version of specifications for the new pump), I would interpret this as saying the maximum GPM would be 45 (for 1.5 inch) regardless of the head feet.
Am I reading this correctly? And if so, does that mean my new 1.5 hp pump can not deliver as much flow as my old 1 hp pump?

 

[mas985]

17 PSI would be fairly high for the MaxFlo VS at 3000 RPM which is the max RPM. Assuming the pump is at water level, that is around 42' of return head and suction head would be between 2-10' of head depending on the configuration. So at best that is around 60 GPM which is pretty good for that pump.

When you switch on the vac, how does the filter pressure change?

But with regards to your last post, for most 2" plumbing setups, the Maxflo VS will deliver more flow but not by much. For your plumbing, they will probably be about the same.

 

[DanielP]

The first image is for the old pump. If I read it correctly, it says I should get about 50 GPM with 40 head feet.
The second image is one version of specifications for the new pump. If I read it correctly, this says I could get 75 GPM at 3000 rpm with 40 head feet, but I assume this is with 2" piping.

Although pipe size is taken into consideration when determining feet of head, the two charts are directly comparable because, at that point, you have already determined feet of head.

So, looking at the third image (another version of specifications for the new pump), I would interpret this as saying the maximum GPM would be 45 (for 1.5 inch) regardless of the head

No, the last chart is recommendations for the maximum flow you want to push through a certain size pipe. It does not affect how you should interpret either chart, nor is it a "speed limit" even though it does slow the flow rate down by increasing resistance. The resistance is accounted for when you calculate the total feet of head so it's not important to know pipe size after you've calculated feet of head.

If you have >= ~51 Feet of Head, the old pump is better, at 55 Ft it is much better. Are you sure you only have 40 Feet of Head?

55 Ft:
Old: 30 GPM
New: 16.5 GPM

52.5 Ft:
Old: 37.5 GPM
New: 31 GPM

Hopefully someone will chime in and help you determine your total feet of head because I'm not good at it. If you do have >51 feet of head, hopefully the old pump was good and is compatible with your new motor.

 

[mas985]

In most cases, you cannot directly compare head loss between pumps unless they have identical head curves. When you change pumps, the head curve changes so the operating pont, both head and GPM, will change. So comparing GPM at the same head loss would be incorrect. If you know the plumbing curve, you can plot that over both head curves and find the operating point for both pumps on the same plumbing.

However, in this case, there is one cross point in the head curves where then are the same.

Based upon measurement data which is slightly different than the published pump curves, both pumps have the same operating point at 53 GPM and 47' of head. But the head curves deviate around that point so to the left the Superpump, which is a higher head pump, does better. But to the right of that point, the MaxFlo does better because it is a lower head pump.

 

[Merccooper]

Thanks for your help guys, it is very much appreciated. I usually think of myself as someone who catches on to things pretty quick, but this stuff has me scratching my head!

So in reply to Mark's question "When you switch on the vac, how does the filter pressure change?": the PSI actually dropped by about 3 PSI. I thought at first it was because I got air in the line when putting the vac hose in, so I vacuumed for about 10 minutes (boy, it is cold outside!) to clear the line. It cleared a little, but I think there is a suction leak at the skimmer (I diagnosed that earlier, but thought I was wrong, listening to it again now when vacuuming, I could hear the air again, also, there was air in the filter basket). So, I guess is part of my problem. (although, when the pump runs for about an hour, the suction leak stops!)

With regards to the feet of head....I really don't know how much I have (I thought I did), but looking at it now I guess I need to try and more accurately figure it out.
Isn't "feet of water" or "Total feet" an aspect of the pool configuration? So, regardless of the pump, I would have xxx "feet of water" which is what impacts the capacity(GPM) that the pump is capable of of?

So if I look at the two curve charts I have posted (sounds like you have a different spec sheet Mark) and if I assume a couple of different scenarios:
Total head of 20:
----then Super Pump has about 75 GPM
----then Maxflo has 100 GPM

Total head of 40:
----then Super Pump has about 45 GPM
----then Maxflo has 75 GPM

Total head of 60:
----then Super Pump has about 10 GPM
----then Maxflo is not capable of pumping

I must be reading this wrong because I get a different understanding than what you are saying Mark.
Mark, where did you get the "measurement data"? It sounds like it has more accurate information.

 

[mas985]

Why do you care what the head is and what the flow rate is? In the end, it doesn't really matter.

I don't have a different spec sheet. I use the APSP/CEC pump measurement data which is real. Published pump curves are usually theoretical so they may not always match.

But again, you can't compare two head curves at the same head loss because the two pumps will not have the same head loss for the same plumbing. Head loss is dependent on flow rate. So the higher the flow rate the higher the head loss and to find the operating point of any pump you need to find where the plumbing curve crosses the head curve.

To better understand pump head curves and how they relate to plumbing head curves, you may want to read the sticky link in my signature that I wrote called "Hydraulics 101".

 

[DanielP]

I think what he's saying is that you can't assume the new pump will always out perform the old pump just because the new pump has a higher flow rating at a single measurement point. The reason that the new pump beats the old pump at 40 ft of head but is worse at 55 ft of head is because they have different head curves. The new pump is optimized for higher flow, sacrificing head loss. The old pump is optimized for higher head, sacrificing flow. If they had the same head curves, whichever pump was better at one measurement would also be better at any other measurement.

Assuming nothing else happened between the time the old pump was working great and the new pump being installed, the problem is the pump curve.

I said you may be in luck if the old motor was bad and you could just put the old pump on the new motor. Truth is, the old pump was probably rated at 3450 RPM and not 3000 RPM so it may not be any better than the new pump on the new motor, and it (old pump on new motor) would certainly be worse than when it was on the old motor.

 

[mas985]

I don't think the problem has anything to do with the head curve. I think it is a simple case of the plugged suction line. Although 17 PSI would indicate very high flow so there is some conflicting data. Has the filter been backwashed recently? Also, what was the old pump's filter pressure?

But a picture is worth a thousand words. Here is a set of pump head curves overlaid with a set of plumbing head curves. Where each pump curve intersects with a plumbing curve is an operating point. As you can see, each pump has a different operating point for each plumbing curve. So you really can't look at a pump's head curve without considering the plumbing curve. BTW, your plumbing curve is probably close to Curve-A. That is typical of 1.5" plumbing. That also happens to be at the point where the SuperPump crosses the MaxFlo VS head curve so for that plumbing curve, the flow rates and head loss are the same. But even if your plumbing was Curve-B, the difference in flow rates between the two pumps is not all that different.

 

[Merccooper]

Thanks again for all your inputs guys, I know it takes a lot of work and it must be frustrating dealing with people like me! It is appreciated though. I think I'll have to by a t-shirt.

I guess at this point I will fix the suction leak at the skimmer and see how things work after that. I guess my concerns really come from two things and a miss-expectation:
1. The vac suction using the new pump is not that great.----------Hopefully fixing the skimmer suction leak will mitigate that.

2. Since the vac suction was low and I can see and feel the flow at the returns is not as much as the old pump, I thought I wasn't getting the flow needed.----------Through my informal test of filling a bucket, I estimate I'm getting 45 GPM @ 3000 rpm which is more than enough for 3 turns per day. I can later fine tune this for the minimal GPM to save costs.

Missed expectation: When I bought the pump I was under the impression that I would have much more flexibility (able to have lower rpm and higher flow rate, able to select the best rpm for my vac (which I can, but turns out to be the highest setting)). I guess may still have some of this flexibility once I get things cleaned up and become more familiar with the pump. In the end, I wish I had visited this site before my purchase!

Again, thanks for all your input.
I think I'll be doing this for a while longer!
.

 

[mas985]

First, you don't need anywhere close to 3 turns per day. I have less than a 1/2 turn per day. You might read this for some background on what is actually needed for pump run time: http://www.troublefreepool.com/content/152-determine-pump-run-time.

Also what was your old pump pressure without the cleaner?

And is there only one suction line from the pool to the pump?

 

[Merccooper]

Wow, thanks for that link. I guess I should go back to Pool School and read everything from the start.
I think, but no sure, the pressure was at around 20 with the old pump.

There are two suction lines, one for the drain and one for the two return jets.

 

[mas985]

There are two suction lines, one for the drain and one for the two return jets.

Return jets are not on the suction line, they are on the return line. My question was about the suction side plumbing only. Is there a separate pipe for the main drain and skimmer from the pool all the way to the pad? They would combine before going into the pump via a TEE or a 3-way valve at the pad. Or does the main drain combine with the skimmer at the pool and then there is only one pipe back to the pump?

[EDIT] I did some calculations and assuming one suction pipe and one return pipe, the pressure you are seeing is very high for that setup. It means there is an extreme amount of head loss on the return side of the plumbing for either pump. The plumbing curve is close to Curve-B and not Curve-A as I originally thought.

Do you trust your pressure gauge? Does it go to zero when the pump turns off? Also, what size eyeballs are in the return jets?

 

[DanielP]

Is it possible the old plumbing allowed for the main drain to be closed while trying to vacuum from the skimmer and the new plumbing doesn't allow you to close the drain so you get full suction from the skimmer?

 

[Merccooper]

Sorry guys, I had a mental gap on my last post. I had meant to say;

There are two suction lines, one for the drain and one for skimmer (yes, they join at a three way valve at the pump).
There is one return line that splits near the pool to two two jets.

 

[mas985]

So based on that, if your old pump was producing 20 PSI, then the MaxFlo VS should produce around 18 PSI so that is not far off from reality. But that also means the operating point for the new pump is around 39 GPM @ 50' of head and the old pump was around 40 GPM @ 55' of head so not all that different. But that is a lot of head loss for that flow rate so there is some significant head loss in the return side of the plumbing (for both pumps).

Again, what is the size of the eyeballs in the returns (diameter of the hole)? I am just trying to figure out what could be causing so much head loss. Does the filter have a bypass mode? And can you tell if the flow increase substantially in that mode?