Re-plumb to improve flow rate?

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B

bjohannes

Well-known member
May 11, 2017
59
East Gwillimbury ON
I've never been thrilled with the plumbing job that my pool builder did in 2017. The equipment pad is about 6.5' above the water line, so the pump (SP23520VSP) has its work cut out for it. I find myself having to run the pump at 90% or more to keep the heater flow sensor happy. When the filter (DE4820) gets even a bit dirty, even 100% pump speed may not be enough to maintain the minimum flow rate for heating.

I've noticed that I could reconfigure the equipment layout and eliminate four 90 degree bends simply by rotating the filter 90 degrees and having the lines go straight into the multiport valve. I could probably also do away with the two 90s that are just upstream of the heater. Would doing so improve my flow rate significantly? Is there any reason not to make these changes?

IMG_20210525_194635.jpg

IMG_20210525_194656.jpg
 
B,

I doubt that you would even be able to tell any difference between what you have now and your proposed setup.. :scratch:

Something is not right, but I doubt that a few 90's are your issue..

What HP is your pump?

Let's see if we can get one of our flow guys to chime in...

Thanks,

Jim R.
 
His plumbing appears to neck down from 2" to a 1.5" section right before it splits for the returns.... it looks like there is a reducing fitting immediately after what looks like a SWG cell. That has got to be restricting the flow.
 

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IUsedToSail said:
His plumbing appears to neck down from 2" to a 1.5" section right before it splits for the returns.... it looks like there is a reducing fitting immediately after what looks like a SWG cell. That has got to be restricting the flow.
Click to expand...

I,

It appears to me all his "pool" plumbing is 1.5" except a few things at the pad.. If that is true, it won't make much difference

Jim R.
 
What is the filter pressure at full speed?

Is the pump wired to 115 or 230 volts?

If you can get a vacuum reading that would be helpful.

If you added a flow meter, that would help diagnose the issue.

If you can convert the filter pressure and vacuum pressure to feet of head, you can see what the expected flow rate is supposed to be at the below speeds.

For example, if the vacuum plus filter pressure is 20 psi, the total head is about 46.2 feet.

If we look at 46.2 feet of head and 115 volts, the flow is expected to be about 37 gpm.

If the pump is receiving 115 volts, the top speed is reduced to limit the maximum amps as shown in the black dotted line.

How far is the pump from the pool?
Pump Curve MAXFLO VS 500.png
 
bjohannes said:
The equipment pad is about 6.5' above the water line, so the pump (SP23520VSP) has its work cut out for it. I find myself having to run the pump at 90% or more to keep the heater flow sensor happy.
Click to expand...
Part of the problem is that the heater does not have a flow switch, it has a pressure switch.

Because the heater sits so far above the water, the pressure in the heater is significantly reduced and the flow has to be much higher than normal to activate the pressure switch.

I would switch to a flow switch instead of a pressure switch.

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IUsedToSail said:
His plumbing appears to neck down from 2" to a 1.5" section right before it splits for the returns.... it looks like there is a reducing fitting immediately after what looks like a SWG cell. That has got to be restricting the flow.
Click to expand...
Good catch, I think you're right. I'll check in the morning, but I'm pretty sure all of the other plumbing is 2" (except the main drain and the returns).
 

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JamesW said:
What is the filter pressure at full speed?

Is the pump wired to 115 or 230 volts?

If you can get a vacuum reading that would be helpful.

If you added a flow meter, that would help diagnose the issue.

If you can convert the filter pressure and vacuum pressure to feet of head, you can see what the expected flow rate is supposed to be at the below speeds.

For example, if the vacuum plus filter pressure is 20 psi, the total head is about 46.2 feet.

If we look at 46.2 feet of head and 115 volts, the flow is expected to be about 37 gpm.

If the pump is receiving 115 volts, the top speed is reduced to limit the maximum amps as shown in the black dotted line.

How far is the pump from the pool?
View attachment 337547
Click to expand...

Pretty sure it's wired for 230 volts. I just completely disassembled the DE filter, fully cleaned and soaked the grids (dishwasher detergent then 10% muriatic acid) then reassembled and added fresh DE. Filter pressure now reads 8PSI at 100% pump speed.
JamesW said:
Part of the problem is that the heater does not have a flow switch, it has a pressure switch.

Because the heater sits so far above the water, the pressure in the heater is significantly reduced and the flow has to be much higher than normal to activate the pressure switch.

I would switch to a flow switch instead of a pressure switch.

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HomePool & SpaPool & SpaHarwil Flow Switches are used by almost all of the major pool equipment and spa manufacturers in the world. Harwil Flow Switches are a critical part of the new generation of salt water chlorine generators which are used to replace adding chlorine to a swimming pool. The...
harwil.com harwil.com
Click to expand...
Can you swap the pressure switch for a flow switch in a Hayward NG heater?
 
IUsedToSail said:
His plumbing appears to neck down from 2" to a 1.5" section right before it splits for the returns.... it looks like there is a reducing fitting immediately after what looks like a SWG cell. That has got to be restricting the flow.
Click to expand...
Would I just replace the part after the SWG with a 2" section and 2" tee, and use a 2" to 1.5" adapter on the returns?
 
You can install a flow switch in the line going to the heater and connect it to the wires that would normally go to the pressure switch.

Below, you can see the SWG salt cell flow switch (marked F) and where to install a new flow switch (Also marked F).

The flow switch goes in a T with a 1/2” npt female thread like the one for the SWG salt system.



Install flow switch.

Remove wires from pressure switch.

Connect wires from flow switch to wires that were on the pressure switch.

aquarite flow switch with T.jpgInkedSystem flow switch_LI.jpg
 
The flow switch need to be set to trigger at about 10 gpm per 100,000 btu/hr of heater.

A 200,000 btu/hr needs 20 gpm.
a 400,000 btu/hr heater needs 40 gpm etc.

Contact Harwil for the right flow switch that will fit in the 2" T with a 1/2" female thread.

The Aquarite SWG flow switch triggers at about 15 to 20 gpm, so it won't be a good choice for a bigger heater like a 400,000 btu/hr.
 
bjohannes said:
Yup, this was from scratch. I feel like he just used whatever parts he had at the time. The check valve was added later on (but probably should have gone ahead of the pump somehow).
Click to expand...
I can see why you weren't thrilled. There's no excuse for a professional to do a plumbing job like that, especially considering it was a new build. To put flex pvc plus a hose clamp in front of the pump like that boggles my mind. Why would he not just run a longer piece of straight hard pipe right into the the coupler?

It looks like he used all flex pvc underground, which is not the way to go. He could have at least come out of the ground perpendicular and made it look professional. That flex piece coming out of the 90 elbow of the pump discharge is gonna fail eventually with all the downward weight from being filled with water. I'd replace that sooner rather than later.
 
Each heater maker makes a flow switch for their heaters. Hayward, Raypak, Pentair etc.

Some come with different paddles that allow you to adjust the trigger flow by changing the paddle.

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114400 - McDonnell & Miller 114400 - FS4-3, 1" General Purpose Flow Switch - Paddle Style

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