Pump Efficiency and Head Loss... I’m at a Loss :(

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T

TxHr

Bronze Supporter
Sep 6, 2018
66
New Braunfels, TX
Pool Size
17000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello Everyone,

We have recently completed our new pool build and when we installed our Pentair Intelliflo VSF I was excited to see the ScreenLogic app displayed the wattage, RPM and flowrate. My excitement quickly dwindled as I noticed my pump was running at 3000 RPM pushing a whopping 54 GPM. It seems I’m having to run a higher than expected RPM to achieve the desired flow.

I read Hydralics 101 prior to our build and when I contracted with my PB, I specifically asked about Hydralics, head loss, etc and he assured me we would have an extremely efficient system. Our PB builder used 2” lines for the returns and most of the length for the floor drain were 2.5”, with two skimmers independently plumbed using 2”.

My pool setup consists of the following:
Pentair VSF pump
Pentair Quad DE 60 filter w/ multi-port valve
Pentair Ultratemp 120 HC heatpump
4 returns w/ 3/4” eyeballs
2 skimmers, plumbed independently
1 Line for suction cleaner (plumbed as 5th return in an attempt to reduce TDH).
1 main drain (dual drains in T)
17,000 gallon rectangular pool
3.5’ – 6’ deep

The equipment pad is 10’ from the pool and 8” below the surface of the water. The base of the pressure gauge on the filter is 28” from the surface of the water.

The heater is plumbed into a 3-way valve and the chart below was taken w/ the valve sending ½ the water to the heater and ½ the water through the bypass:


RPMPSIGPM
10000Below 15 GPM
1250121
1500328
1750535
2000742
22501047
25001252
27501456
30001861
32502066
34502369


On paper, everything appears to be picture perfect but nothing is adding up and I’m at a loss. This is our first pool and unfortunately plumbing and I don’t always get along. I was trying to build the most efficient pool but according to the folks at Pentair I’m running a high total dynamic head and my pump isn’t running as efficient as it should. I’m at a loss at what to do. There isn’t a significant amount of elbows (or at least I don’t think there is). I’ve read every thread on TFP I could get my hands on and I’m still confused what to do or where to start, hence the reason for my post. Any advice or direction would be greatly appreciated.


Thanks in advance,


Brandon

Link to GoogleDrive for pics of plumbing:
https://drive.google.com/drive/folders/1z0kdz7g0S7ZZZMu3efw743_rlFSgcd3M
 
Brandon,

I can't help with the technical part of this, but I'm not at all sure what you are tying to accomplish???

If you can run your pump at 1250 RPM with a filter pressure of 1, it will cost you less than $20 bucks a month, if you run 24/7.. running less, will cost even less.. How efficient do you want to be..?

I guess my point is, you really don't need to know the TDH to have fun in a pool... :p

It does not appear that you have any water features, so why the desire or need to run 54 GPM???

Thanks,

Jim R.
 
Hi Jim,

We have three bubblers on our sun shelf that will be used infrequently. When I spoke with Pentair, they said I needed to run 65-80 GPM to my heatpump to heat or cool the pool. I can’t get more than 69 GPM and that’s with bypassing the heatpump with half of the flow. When I was running the pump at 3450 RPM and sending all water to the heater I my flow was reduced by 7 GPM. Pentair Tech support was confused and said my head is calculating around 75-80 and usually they see 45-50. They advised I get with my builder, as something didn’t seem right.


Thanks,

Brandon

- - - Updated - - -

JamesW said:
Is the pressure from the filter pressure gauge or from the pump display?

IntelliFlo VSF Variable Speed And Flow Pump (Keypad Overview) - YouTube
Click to expand...

Hi James,

The PSI is from the filter gauge and the flow is from the Pentair Screenlogic app.


Thanks,

Brandon
 
Check the psi from the pump display as shown in the video and compare to the filter pressure.

The pump measures total psi from suction and pressure side.

So, the pump pressure minus the filter pressure will indicate the suction pressure, which will help us evaluate the problem.

Also, the heat pump does not need that much flow.

What does the manual say for min/max flow rates?

I'm seeing that the minimum flow required is 30 gpm. 30 to 40 gpm should be plenty of flow.
 
Hello Again James,

Thank you for the lesson on pump operation. The more I use the menus, the more I am impressed of all the features that are baked into these devices.

Here is the pressure information you requested:


RPMGPMFilter PSIPump PSISuction PSI
1000Below 15 GPM033
125021143
150028374
175035594
2000427125
22504710155
25005212197
27505614239
30006118279
325066203212
345069233613

The UltraTemp 120 H/C requires a minimum flow of 30 GPM and a max flow of 100 GPM. According to Pentair Tech Support, they recommended 65 GPM and would prefer 80 GPM.

Thanks again for all of your help. I’m interested to see what the numbers tell us and where we go from here.


Thank you,

Brandon
 
Last edited:
The head loss the pump is experiencing is worse than a typical pool with 1 1/2" plumbing so something is severely restriction flow, especially before the filter. My suspicion is that it could be the multi-port valve on the DE filter or something on the suction side of the pump. Can you put the filter into re-circulation mode and report back the "pump pressure/GPM" at full speed?

The return side is above expected as well but let's see what re-circulation does.
 
The heat pump has an internal bypass. Anything over about 40 to 50 gpm will be bypassed.

So, anything over about 50 gpm will go through the bypass and won't go through the heat exchanger, which means that it will not affect the performance.

The manual has a graph of the flow vs psi that shows an exponential increase between 20 and 50 gpm and then the graph levels off.

In my opinion, the ideal flow rate is about 35 to 45 gpm.

The suction can be roughly approximated by about 92 feet of 1.5" pvc pipe

The return can be approximated by about 170 feet of 1.5" pvc pipe.

Both indicate an excessive restriction.

Are the pump and skimmer baskets clean?

The inline chlorinator is a bad idea. It creates a lot of flow restriction.

You might have some sort of clog in the suction and/or returns.

Are the readings with all flow going through the heat pump?

Are the skimmers and main drains both open?
 
mas985 said:
The head loss the pump is experiencing is worse than a typical pool with 1 1/2" plumbing so something is severely restriction flow, especially before the filter. My suspicion is that it could be the multi-port valve on the DE filter or something on the suction side of the pump. Can you put the filter into re-circulation mode and report back the "pump pressure/GPM" at full speed?

The return side is above expected as well but let's see what re-circulation does.
Click to expand...


Mark,

I believe that Quad filters are plumbed different than most filters and also take a different multiport valve... If the pool builder plumbed it wrong, or used the wrong MPV, would that cause the problems Brandon is seeing???


Brandon,

Pics of the filter in/out and a pic of the MVP part number would rule it in or out..

Thanks,

Jim R.
 
Jimrahbe said:
I believe that Quad filters are plumbed different than most filters and also take a different multiport valve... If the pool builder plumbed it wrong, or used the wrong MPV, would that cause the problems Brandon is seeing???
Click to expand...
Yes, that was my first thought as well but I could not find a port diagram to confirm. If it is plumbed backwards, then it would support some of the numbers we are seeing. One way to tell is to put the filter into recirculate and see if the numbers change quite a bit.
 

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You should be able to find the multi port valve P/N on the unit. Quad’s have their own specific MPV’s and they are DIFFERENT than the Pentair sand filter MPV’s. Also, when I discussed an MPV with my pool builder long ago, he threw cold water on the idea as he said - (1) I’d never need it, (2) They’re another thing that can leak, needs maintenance, etc., AND (3) The quad MPV’s add a lot of head loss. I believe Pentair has since changed the MPV’s to improve their head loss and they even make larger diameter MPV’s, but, either way, a Pentair sand filter MPV will definitely not work properly with a Quad filter.

Also, I consider the Quad 60’s to be kind of small. I specifically got the oversized QuadDE-100 and I believe they even make a 120 sq ft Quad filter now. If the QuadDE-60 was overcharged with too much DE, that could definitely impact performance.

When was the last time you opened the filter?
 
The quad de multiport is the same as the sand filter multiport.

It's different from the regular de multiport, which often causes confusion.

I suspect that it might be the wrong multiport. The model number will confirm.

There's a silver sticker on the vertical pipe coming out of the front bottom of the multiport. The part number should be 261050.

If the part number is 261142, it's the wrong multiport.

Looking at the cartridges can also be helpful.

I would eliminate the multiport.

Backwash doesn't work and waste can be accomplished by using a 3 way valve between the pump and the filter.

The multiport manual has a head loss curve, which show the effect of the multiport on head loss vs flow.

It's not horrible or good, but it's unnecessary in any case.
 
Thank you for all of the responses. I can’t tell you how much I appreciate everryone’s Efforts to diagnose and fix my flowrate issue(s). Please see the responses to the questions below. If there is anything else needed, please let me know. I have also attached new, daylight, photos to the GoogleDrive link below.


Are the pump and skimmer baskets clean? The skimmer baskets and pump is clean. Filter was backwashed on Monday and fresh DE added.


The inline chlorinator is a bad idea. It creates a lot of flow restriction. It’s also installed in the wrong location :eek:


You might have some sort of clog in the suction and/or returns. I was wondering if this could be the case and how one would go about investigating this


Are the readings with all flow going through the heat pump? ½ the flow is through the heat pump and ½ through the external bypass. Apparently my PB forgot to plumb the chlorinator to the return side of the heat pump, so if we need to try a test sending 100% through heater, I can do that. I’m just not sure the chlorinator is the culprit, but I’m open to anything at this moment.


Are the skimmers and main drains both open? Yes, both skimmers and the main drains are open. I tried closing the main drains and just running skimmers, the GPM was only affected by a 1 GPM loss (in recirculate, 2500 RPM, 55 GPM w/ mains and skimmers vs. 54 GPM w/ just skimmers or mains).


When was the last time you opened the filter? I have never opened the filter, it’s less than a month old and hadn’t figured there was a need.


“Pump pressure/GPM" at full speed? 3450 RPM, 86 GPM, 35 PSI on pump


Model number for the multi port valve: 261050

LINK to Plumbing Photos
https://drive.google.com/drive/folders/1z0kdz7g0S7ZZZMu3efw743_rlFSgcd3M
 
The check valve going to the heat pump looks odd. What brand is it?

Is it pointed in the right direction?

Can you see the flapper lift up with flow?

What happens if you put all flow to the heater vs all through the external bypass?
 
mas985 said:
This is inconsistent with the table above. There you had 69 GPM.
Click to expand...

This was with the valve in recirculation mode. The table above was the valve in filter mode

- - - Updated - - -

Jimrahbe said:
Brandon,

Did you ever put your MVP in the recirculate position like Mark requested???

Jim R.
Click to expand...

Yes, that’s where I got 86 GPM at 3450 RPM with a pump PSI of 35

- - - Updated - - -

JamesW said:
The check valve going to the heat pump looks odd. What brand is it?

Is it pointed in the right direction?

Can you see the flapper lift up with flow?

What happens if you put all flow to the heater vs all through the external bypass?
Click to expand...

There isn’t a check valve going to the heat pump, the one that is on the back side of the heater is a new “flapper” check valve that goes to the returns from the heater. I’ll go out and get some data with the flow going 100% to heater and 100% to bypass
 
86 is much more reasonable and closer to what I would expect with that plumbing. Given the difference in flow rate, there is something wrong with the filter setup. Likely the MPV.
 

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