Filter Pressure Too High...?

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mculik5

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Oct 18, 2016
66
Long Valley, NJ
After backwashing, my pool's filter (Hayward S244T sand filter) is running at 28 PSI according to the gauge. Additionally, at max speed, the pump is only moving ~32 GPM (according to my flowmeter), which translates to about 73' of dynamic head according to the pump performance charts.

The pool is 20' x 40'. The plumbing is very simple - just a pump and filter, wall suction inlet, skimmer inlet, and two returns. The pump is near the pool. Based on the size of my pool and what I've read about figuring out dynamic head, I have a hard time believing the 73' number.

Also, I noticed while backwashing today that the pump inlet check valve, which normally looks just barely open, was almost fully open. To me, this indicates that the suction side plumbing is in good shape, and the issue is some kind of blockage on the return side. Thinking the filter was the culprit, I tried it in recirculate mode, but performance was only slightly better - ~35 GPM.

To me, this indicates the problem is some kind of blockage on the return side after the filter, but the only things downstream, as far as I know, are pipe, a flowmeter, a union, and the return ports.

Separately, if I run the pump at a slower speed, the filter shows ~10 PSI and the flowmeter ~20 GPM. However, running at this speed results in a big air pocket (much bigger than a bubble) at the top of the pump strainer basket, although the pump never loses prime or sucks straight air. Also, this air pocket is not an issue when running at full speed.

Only other weird thing I noticed is that while recirculating, a fairly steady stream of drips was coming out of the backwash site glass, although the site glass itself was not filling up.

Lastly, the sand was changed last year, and the pressure has been creeping up all season (started at 26 PSI) regardless of backwashing.

Any ideas about what might be going on? Would love to get my setup running as efficiently as possible.

Thanks.
 
Do you know what RPM your pump is running at? That's awful high pressure for a 1.5hp pump and a S244T - Is your pressure gauge reliable? How is the flow/pressure at the returns in the pool? What was the pressure before the sand was changed last year?
 
The stats quoted above - ~32 GPM/28 PSI are at 3450 RPM. I also mis-quoted the low RPM stats above. At 1650 RPM, the pump is moving ~17 GPM/8 PSI.

I haven't tested or replaced the gauge, but it moves up/down smoothly as I change the pump speed, registers 0 when the pump is off, and is stable when the pump is running at a constant speed. Also, the flowmeter was new last year. It's a FlowVis.

The flow at the returns is what I'd call "normal." This is my first pool, so I have no basis for comparison, but when the pump is running at high RPM, the flow is strong, but not crazy - stronger than a garden hose for sure, but nowhere near a pressure washer, if that's helpful.

Based on a post I made on this forum last year, the pump was moving 48 GPM / 21 PSI at 3450 RPM just after I installed it and the new sand, but even that seems like high pressure/low GPM for my plumbing setup based on the performance curves (equates to ~62' of dynamic head).

Also, like I said above, when backwashing, the check valve before the pump is WIDE open, which means the pump is moving a ton of water. When filtering the check valve barely looks open. That tells me the pump and suction plumbing can support tons of flow, and something downstream of the pump (filter and/or return plumbing) is causing the high pressure/low flow...I just have no idea what (although similar numbers when using recirculate seem to indicate it's not the filter).

Could it be the multi-port valve? How often do blockages or other issues happen to return plumbing that's in the ground (and has been for 18+ years). Also, seems to be getting worse, given that last year it was running 21 PSI with clean sand, and now it's running 28 PSI after backwashing.

Thanks!
 
Maybe a pic of the plumbing will help.
How many returns?
How big are the eyeballs?
Have you removed them to see if there is anything caught behind them?
Any valves after the pump or filter?
Have you opened them to see if some debris got by?

Pressure going up in recirc doesn't make sense.
 
Thanks for your replies. Since I figured it would be easier and clearer than pictures and text, I made a quick video this morning that shows my plumbing and the issue that I'm seeing.

Pool Plumbing - YouTube - It's a little long, but covers everything.

@duraleigh - The PSI in bypass/recirculate mode is same as when filtering - ~29 PSI. This is shown in the video.

@pooldv - Plumbing is covered in the video. Two returns - 1.5" PVC, and the eyeball outlets are probably 1" in diameter. It's not shown in the video, but I removed both of the return fittings completely, and the pressure/GPM didn't change, nor was there any junk behind them. No valves after the pump or filter.

Again, thanks for the help!
 
mculik5 said:
Thanks for your replies. Since I figured it would be easier and clearer than pictures and text, I made a quick video this morning that shows my plumbing and the issue that I'm seeing.

Pool Plumbing - YouTube - It's a little long, but covers everything.

@duraleigh - The PSI in bypass/recirculate mode is same as when filtering - ~29 PSI. This is shown in the video.

@pooldv - Plumbing is covered in the video. Two returns - 1.5" PVC, and the eyeball outlets are probably 1" in diameter. It's not shown in the video, but I removed both of the return fittings completely, and the pressure/GPM didn't change, nor was there any junk behind them. No valves after the pump or filter.

Again, thanks for the help!
Click to expand...

When you backwash, you are running "through the filter"... yet you still have ~10PSI. This tells me that your restriction/blockage is somewhere in your return plumbing between the filter and the pool.
 
The pressure gauge is installed on the multi-port valve. The only openings in the filter housing itself (the brown barrel in the video) are the big opening at the top that the multi-port valve sits in, and the drain plug at the bottom. I believe the gauge on the valve is standard fitment. It's not jury rigged.

Also, I'm apt to trust the pressure gauge based on the facts that it, plus the check valve and flowmeter, are all showing the same things and moving together.
 

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@JimMarshall - I agree that it's in the return plumbing. Guess the only option is to snake it?

How common are underground return plumbing problems? What are typical problems? The pool isn't losing water, so I don't think it's a cracked pipe. Could it be a "kink" or something like that?

Also, any chance it's the multi-port valve? Maybe something not moving correctly inside the valve that is causing the filter and recirculate ports not to open fully? Does that ever happen?

Thanks!
 
First, your video is FANTASTIC. You show the issue perfectly.

I think you have an issue with your multi-port valve......here's the giveaway to me.....

In recirculate, the water goes thru the pump, through the multiport, and back to the pool. It bypasses the most resistant thing in you system - the filter. So, normally in recirc, you would get a drop in psi at or maybe even below your backwash pressure......not 28-29 that you are getting.

You backflow valve is an indicator, too. It shows you have far less flow in recirc than you do in backwash when they, in fact should be about the same.

I would suggest you disassemble the multiport and inspect it's innards.......I think you will find your answer there.

PS - you take nice care of your stuff. I think your gauge is working OK, but you would REALLY like the 12 dollar gauge at TFTestkits. It's much easier to read and glycerin filled so it won't freeze in the winter.

PPS - very nice work on your water quality.
 
With me not having and not being very familiar with sand filters and multiport valves, I had not considered it as a point of restriciton, but I think that Dave is onto something here. That's certainly where I would start, especially since unless something has happened (think, something drove over that area and crushed pipes, you dropped something down the pipe while the union was torn apart, etc), I would consider it very unlikely for you to have a blockage in the return pipes... I think the multiport valve is the more likely culprit. I know that they make rebuild kits for them, you may want to consider picking one up before you tear into it
 
Agree with all that, Dave. Good stuff and nice pool!

Also, I believe it is recommended to always turn the multipart valve either clockwise or counterclockwise to help the spider gasket last longer.

If the multiport valve doesn't end up being the problem the next problem could be collapsed flexible PVC underground. Sometimes, PBs use flex PVC underground and sometimes it collapses. Using a plumbing snake to check for blockage is a good idea.
 
Thanks a ton!

Will check the multi-port valve tonight.

@pooldv - How common are collapsed pipes? Is there a fix that doesn't require digging? I'm almost certain we have flex PVC in the ground based on what was coming up by the pump/filter when I re-plumbed. There was an oil-tank in the ground that was removed right before we bought the house that was behind the sidewall return that I point out in the beginning of the video. There's several feet between where the oil tank was and where I'd expect the plumbing to be, but maybe the soil disturbance partially crushed it? We put a patio where the oil tank used to be, but that didn't require much digging or heavy machinery, and we waited a year before installing to allow the soil to settle.

I found the pool inspection report from when we bought the house, and the pressure at the time (BEFORE oil tank was removed; also with old sand and no idea how dirty/when last backwashed) was 18 PSI. However, this was with a 1HP pump (Hayward Super SP2607X10). Does it seem feasible that upgrading to the new, 1.5 HP pump that moves more water could cause the 10+ PSI jump in pressure? Here's a sample of GPM differences:

GPM
Feet of HeadHayward (Old)Pentair (New)Difference
20749731%
30648736%
40547641%
50406460%
601352300%
 
Hope for the best that it is the multi-port. If not, then you are sorta stuck with a collapsed pipe as the source and that is gonna' require digging. It is quite rare but it does happen.

Upgrading your pump is not the cause of your psi increase......it is the restriction on the pressure side that is causing it.
 
Re: Filter Pressure Too High...? - UGH!!! Crushed Pipe

No such luck with the multi-port valve. Took it apart tonight and it's fine.

I taped a tiny USB camera to my plumbing snake and made this video...unfortunately...

Blocked Pipe - YouTube

This is approximately 6' of pipe from where I inserted the camera. I can't get the snake or snake/camera past it. About 18" of that pipe is above ground, and of course it continues into the ground a bit before turning laterally. Unfortunately, I can't tell which way the pipe is going, and the initial curve underground that I can see from the top goes perpendicular to where I think it should logically go...

Three questions:

1. Any ideas about what could cause something like this? Based on the 6' of pipe, this is in an area that has been pool deck for a while - no recent digging, heavy equipment, etc.. The only nearby plant is a lilac bush that's partially in a pot (it grew too big and cracked it's way out of the pot, but the root ball is still mostly above ground...and it's just a lilac bush...). Frost heaves, maybe? Also, for what it's worth, the problem seems to be getting worse. Pressure was 18 PSI at max speed with a 1HP pump when we moved in. Based on a post on this forum last year, when I finished installing the new pump (1.5HP), pressure was 21 PSI at 48 GPM at max speed. Now, it's 29 PSI and 32 GPM at max speed.

2. Given that this blockage is in an unlikely spot, what do you think the odds are that there are more crush points further downstream? Looking at the video, does this crush point look tight enough to cause such a bump in pressure?

3. How do you locate the problem spot so that I don't have to play guessing games with a jackhammer? Is there some kind of radio-beacon or inertially guided snake or something?

Thanks!
 
I think the most common cause is improper compaction. Over time settling occurs and crushes the pipe. Flex pipe seems to be the most common by far but schedule 40 rigid pvc can crush and crack as well.

Frost heave? I have lived in the South too long but that seems possible, too.

I can't see the site so you will have to figure your best method of repair. Perhaps you can reroute that line entirely with new pipe and simply disconnect the old.
 
If it’s crushed in one spot it has the potential to be crushed elsewhere. Instead of trying to pinpoint and make a targeted repair, I think I would just run a whole new line
 
Thanks again for all the help.

Lousy outcome, but at least I know what's going on now. If the pipe completely closes, I can run an above-ground line to filter the pool until I figure out a proper fix. Might do that anyway to relieve the pressure on the pump and save some electricity.

For those who have dealt with pool builders before, is it common for them to have horizontal boring machines that allow them to drill horizontally under the concrete? If so, it would be relatively simple to run a line under the grass surroudning the pool and then drill under a few feet of deck.
 

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