Losing flow after a couple hours

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
Hello-

I have an interesting problem and I am not sure what to attribute it to. I opened up the pool last week and I have noticed that, after a a couple hours, I start to lose flow through the system. The return line to the pool starts flowing a lot less and the sight window into the pump basket starts dropping and there is a slow flow of water into it. If I increase the speed on the pump (Pentair VS), the flow will increase but I will see the pressure in the filter rise much higher than it was when I first start it up. It's usually around 10 psi but when I increase the pump speed, I will see it climb up to around 25+ and it still won't have full flow as before.

I thought maybe this was a problem with the filter at first, and usually doing a backwash cycle would reset things and return them back to normal. Last night though, rather than going through a backwash cycle, I shut the pump off, turned the multiport valve (Hayward Vari-Flow XL) to backwash, then turned it back to filter, all without running the pump. When I turned the pump back on, things were back to normal.

Any ideas what this might be? I'm starting to suspect that multiport valve now but then again, I wonder if there's some kind of pressure lock forming in the filter that gets released when I turn the valve? I'm purely speculating there so really I have no idea.
 

mknauss

Mod Squad
TFP Expert
May 3, 2014
18,439
Laughlin, NV
What does your water look like?

So your pump runs fine in recirculate? If so, you most likely have a chemistry issue and have algae.
 

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
I replaced all the sand last year with zeosand so not very old. Water is pretty blue right now but a little cloudy still with some crud here and there at the bottom that hasn’t been cleaned out yet since taking the cover off. I’ve been waiting to get it clear so I can see we’ll enough to vacuum the deep end.
 

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
Yes I do and yes I have a TF100, working on the slam but in the mean time trying to figure out why the flow is so off. I would lean towards what you say however that doesn’t quite add up considering the fact that simply moving the lever from filter to backwash back to filter will make it return to normal operation for a couple hours. Recirculate would be the same as filter mode correct? If so, it works ok for a little while and then slows way down.
 

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
Yes, when I first turn it on in recirculate, the pump primes and the water in the sight bucket fills to the top. The return jet to the pool kicks out a strong full flow that I can see moving the water. After a couple hours, the sight bucket starts to drop, the flow of water coming from the return jet starts to weaken, and you can tell it’s not moving as much water. If I let it run non stop for several hours or a full day, the water flow almost stops completely. The pressure in the filter doesn’t seem to rise unless I turn up the pump speed, at which point I will see much higher pressures than normal but still a very weak flow. Again, I thought it was the filter doing it’s job at first and just needing to be backwashed, but I discovered the other day that moving the valve around seems to release the pressure and doing that without actually running the pump while it’s in backwash will make recirculate return to normal.

I’ve started looking in to air locks because that really seems like what’s happening here. I don’t have any weird rides or dips in my lines though. The inlet side of the pump rises from the skimmer and never goes above the pump inlet, and the return to the pool is similar.

Is there some sort of automatic air bleed that’s usually on a multi port valve or a filter? It seems like getting some air into the system would be unavoidable and it would need to be bled off somehow, so maybe whatever is supposed to do that isn’t working properly? Or maybe I’m just getting too much air in there somewhere, maybe from the valve itself?
 

mknauss

Mod Squad
TFP Expert
May 3, 2014
18,439
Laughlin, NV
If you are losing flow when on Recirculate (to confirm, the MPV is being left on Recirculate continuously) then you possibly have a suction side air leak that is slowly making your pump lose prime. Check the pump basket lid gasket, drain plug orings, etc. Be sure to use pool lube on the gaskets.
 

stargazer1018

Bronze Supporter
Jul 4, 2018
31
SEYMOUR, TN
I was having the same problem the first couple of days after I opened my above ground pool. The cover had gotten blown off during the storm the night before I opened it and all the extra crud on the cover went into the pool water. It had a white flaky stuff covering the water surface. It was too fine to be collected with a net and had to filter through my system. I would notice I started with good pressure but after a few hours I had no pressure. I could turn the pump off and turn it back on and it would get strong again only to lose it again after a short while. After I SLAMed it and got all that crud out it got better.
 

jwhop3

Well-known member
Jun 9, 2014
126
Rocky Mount/Virginia
Heavy sediments will clog sand filters, even with new sand pretty quick. Judicious backwashing is the only solution if sand is new.

I have had issues when putting the recommended or just a touch more sand. If your label is still intact, it should have the amount of sand to add. I used to think this was the minimum, but I'm finding it is the maximum amount.
 

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
So I did some more investigation today. I noticed that there is a slow drip coming from my waste pipe, and I also noticed that I get a loud suction/bubbling noise from the multi port valve area when I first turn the pump on after letting the pressure release. Not 100% sure that’s my problem, but it’s definitely an issue that I need to take care of so I’m going to start with replacing it and see where it goes.
 

jwhop3

Well-known member
Jun 9, 2014
126
Rocky Mount/Virginia
That sounds like a blown spider gasket. Mine was doing the same thing last weekend. I was able to pull out the gasket, it was gooey, but still intact and felt strong. I lubed it with silicon grease and placed back under the multiport. Problem solved, for at least another season. Never a bad idea to order two or three of those at a time.
 

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
Unfortunately the gasket on the Hayward isn’t serviceable. The unit is pretty old, probably original, and feels like the handle is going to break every time I turn it as is. The pure line replacement was only $60 from inyopools so not a huge cost to replace the whole thing. You’re right though, would probably be a good idea to get a spare gasket for the new unit.
 

AngLewis

New member
May 23, 2016
3
Foreman, AR
Unfortunately the gasket on the Hayward isn’t serviceable. The unit is pretty old, probably original, and feels like the handle is going to break every time I turn it as is. The pure line replacement was only $60 from inyopools so not a huge cost to replace the whole thing. You’re right though, would probably be a good idea to get a spare gasket for the new unit.
Did replacing the whole thing fix it? I'm having the same problem. Pressure on my Pentair sand dollar filter will run about 10 psi, after a short while it climbs to 15 psi and return flow decreases considerably. I can backwash and it drops back down to 10 psi for a short while. I have replaced sand this season. Now I've replaced pressure gauge. No bubbles in pump tank lid, do have a suction or pinging coming from port valve.
 

jwhop3

Well-known member
Jun 9, 2014
126
Rocky Mount/Virginia
Did replacing the whole thing fix it? I'm having the same problem. Pressure on my Pentair sand dollar filter will run about 10 psi, after a short while it climbs to 15 psi and return flow decreases considerably. I can backwash and it drops back down to 10 psi for a short while. I have replaced sand this season. Now I've replaced pressure gauge. No bubbles in pump tank lid, do have a suction or pinging coming from port valve.
Ang, that sounds like packed sand. How old is the sand inside your filter? I have the Pentair Meteor, which is similar to your sand dollar, and it was doing the exact same thing you described. I swapped out the sand and she's good as new, I even have ripples in the water now when I rotate the return jets up!
 

jrglenni

Active member
Aug 11, 2017
34
Chelmsford MA
I’m happy to report that it’s been running for about 3 hours so far and still kicking like a champ. On the downside, there is a slow drop coming from the top of the valve so looks like I need to replace it >:|
 

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