Low water flow in returns

[tertelman]

Hello All,

Like so many others, this site and forum have been invaluable resources for me as a relatively new pool owner. This is my fourth season with the pool (came with the house), and I’ve got my chemistry down pretty well. But I do have one issue: This is the second summer I’ve noticed substantially lower-than-normal water flow into the pool from the returns in the walls and floor.

I first noticed this after opening the pool last summer, and that is also when I had a SWG installed (previously used liquid chlorine). Not sure if those two things are related or coincidental. This summer, I replaced the cartridge filters, both because they were pretty worn out (I’m not sure if or when the previous owner had last replaced them) and because I thought it might help with the low flow issue. No such luck.

In addition to the low flow from the returns, I’ve also noticed two possibly related things: 1) There are occasional bubbles—sometimes large, sometimes very small—coming from the returns. 2) The pressure gauge on the filter seems to show a lower psi reading than it used to for the same rpm pump speed, and when I release the pressure valve on the gauge it only dribbles water out (after briefly releasing some air) instead of shooting the water 6-8 feet like it used to.

For what it’s worth, the pool’s original pump died at the end of last season, and I had a new one installed before opening the pool this season. I don’t think this was related to the pressure issue, but I suppose it’s possible.

A couple possible causes of the low flow that I’ve considered: 1) a blockage of some kind between the pump and the filter, causing reduced suction. 2) Normal wear and tear that has damaged o-rings, etc, causing a leak on the suction side. I haven’t really taken action yet to address these possibilities.

Apologies for the long post. I’d greatly appreciate any insights!

 

[reggiehammond]

I would have suspected your filter being clogged up had you not just replaced the filters.
Can you post a picture of your pad? Something isn’t right - perhaps you have a 3 way valve in the wrong position.

Do you have good skimming? Is there air in the pump pot or is it full?

 

[tertelman]

I would have suspected your filter being clogged up had you not just replaced the filters.
Can you post a picture of your pad? Something isn’t right - perhaps you have a 3 way valve in the wrong position.

Do you have good skimming? Is there air in the pump pot or is it full?

Thanks for the reply. I’ll post a picture of the pad in the morning. The skimming is pretty strong when the pump operates at high-ish RPMs, although again I feel like it used to be stronger at the same RPMs. There is air in the pump pot when the pump operates at relatively low RPMs (sub-1800 rpm perhaps). When it operates at 2,000+ RPM, there is no air in the pump pot.

 

[Ahultin]

What was your old pump and what is your new pump?
The bubbles in the return sounds like the gas bubbles formed by the swg.
The air bubble in the pump is typical of a pentair vs pump at low speeds.

 

[tertelman]

What was your old pump and what is your new pump?
The bubbles in the return sounds like the gas bubbles formed by the swg.
The air bubble in the pump is typical of a pentair vs pump at low speeds.

I can’t seem to recall the details of the last pump, but the low flow was observed on that pump as well last season (before it died) and has carried over to the new pump.

 

[tertelman]

Here are a couple photos of the pad

 

[Ahultin]

Your signatures shows intellipro vs-3050, your photo shows superflo vst.
The intellipro, assuming it was your old pump, was 3hp, the superflo is 1.5hp. If correct, this could easily account for lower flow and pressure at an equal rpm.

 

[tertelman]

Thanks, but the lower flow began last summer, when I still had the old pump.

 

[Ahultin]

Taking that out of the mix i would think limits the issue to a latent algea problem, an obstruction in the plumbing or an electrical problem.
Was the flow temporarily restored when you replace the filter cartridges or was there no change?
Do you have a multimeter to test voltage at the pump from line 1 to line 2 (assuming 240v)?
Since you fully close the pool, was the water level dropped and the lines all blown out?

 

[MITBeta]

Can you post a full set of chemistry test results?

 

[tertelman]

Can you post a full set of chemistry test results?

FC 7.5
CC <0.5
pH 7.4
TA 70
CH 330
CYA 60
Salt 4,000

 

[tertelman]

Taking that out of the mix i would think limits the issue to a latent algea problem, an obstruction in the plumbing or an electrical problem.
Was the flow temporarily restored when you replace the filter cartridges or was there no change?
Do you have a multimeter to test voltage at the pump from line 1 to line 2 (assuming 240v)?
Since you fully close the pool, was the water level dropped and the lines all blown out?

There was no/minimal change when I replaced the cartridges, other than the psi going down somewhat on the gauge (as you’d expect with perfectly clean filters). The flow from the returns might have increased slightly, but not significantly. I do not have a multimeter but could pick one up to troubleshoot. The water level was dropped and lines blown out at closing. We get a lot of debris in my neighborhood, so I’m suspecting a blockage of some kind. Or perhaps a missing or damaged seal/o-ring. I will investigate further and report back if I find the culprit!