Constant High Pressure in Hayward Sand Filter

Joeten30

Member
Jun 22, 2017
14
Boston
Happy Summer, ya'll!

Having a little bit of an issue with constant pressure buildup in my Hayward sand filter. Here's what's happening:
- Water chemistry is good. pH 7.4, FC 5, CC 0, CYA 40, CH 210, TA 85. 25,000 gallon in ground pool. Hayward 1 HP pump.

Water is crystal clear and the water level is where it needs to be. The pool was very dirty when I first opened, but I treated it in a timely and effective manor by SLAMing it.
Also, I did not vacuum any debris with a vacuum attached to my system. The vacuuming was done with my robot, and a leaf vacuum that attached to my garden hose, so I'm thinking that there isn't a clog in my plumbing (but, who knows.)

-I initially thought my filter needed to be back washed since the pressure was getting past 20 quickly. I back washed about 4 times before realizing, this wasn't the solution. The pressure would drop down to 10 for a few hours after back washing, but then it would go right back up to 20-24.

-When I run the pool in recirculate mode, the pressure stays at a constant 10. I've been lurking this forum for a while, and I've seen people say that the pressure should be ZERO in recirculate mode. Is this true? I replaced the pressure gauge literally last week... so I'm assuming it's working well. The gauge goes to 0 when the system is off. So I'm confused as to why my pressure is 10 in recirculate mode.

-The return jets seem to be running well even though the pressure is reading high. They aren't as strong as they are immediately after back washing with a pressure of 10 PSI, but they're still moving the water at a decent rate.

A few other things: I had to re-plumb a few fittings before getting my pump back on when opening the pool. At first, there were slight water leaks in the fittings so I cut them and re-plumbed them again and the leaks 100% stopped. I also had a bad drain cap on the bottom of my filter for a few days that was leaking, I had since replaced that and the water stopped leaking there as well.

I believe the pressure buildup in my system is due to air getting in somehow. Maybe it's residual air from the initial bad plumbing or the bad drain cap, but I've since back washed a few times (which should purge out that air).

Also, my Sand Filter is making a weird crackling noise the top of the multi port valve. This noise DOES NOT happen in recirculate mode, just filter mode.

Does anyone know what could be going on? I'm gonna check my pump gasket O-ring, union O-rings and pump drain plugs later today to make sure they're all good. Other than that, I really don't know how air could be getting it. My filter does not have an air purge valve, so I don't even really know how to temporarily relieve the air without back washing and I really do not want to backwash again.

Could the high PSI be happening from something else? Any help would be greatly appreciated.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,003
Tucson, AZ
Sounds like a bad gauge. When you're running in recirculation mode the filter should read zero pressure

Well now I kept reading and you said you replaced it already and it goes to zero in the pump is off. So now I'm a little confused as are you :) perhaps something is wrong in the multi valve? Like the top is misaligned and you are not really in filter or recirculate mode?
 

Joeten30

Member
Jun 22, 2017
14
Boston
Sounds like a bad gauge. When you're running in recirculation mode the filter should read zero pressure

Well now I kept reading and you said you replaced it already and it goes to zero in the pump is off. So now I'm a little confused as are you :) perhaps something is wrong in the multi valve? Like the top is misaligned and you are not really in filter or recirculate mode?
I'm beginning to think the same. Although, it clearly filters the water well, since the water is crystal clear. And it clearly backlashes and rinses fine.
But, the handle on the multi port is hard to move and like I said in my original post, it's making a weird crackling noise.

I'm so confused lol.
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,406
SouthWest Alabama
The fact that the pressure drops after a backwash and then rises tells me that you have something in the water clogging the filter. Have you ran an OCLT to see if there's something that you can't see in the water?

The noise you hear is likely from the air in the system.

The pressure gauge on the Hayward valves are in the pump inlet chamber, so if you have enough restriction in the return path (small eyeballs), you could see a pretty substantial pressure in recirculate mode.
 

Joeten30

Member
Jun 22, 2017
14
Boston
The fact that the pressure drops after a backwash and then rises tells me that you have something in the water clogging the filter. Have you ran an OCLT to see if there's something that you can't see in the water?

The noise you hear is likely from the air in the system.

The pressure gauge on the Hayward valves are in the pump inlet chamber, so if you have enough restriction in the return path (small eyeballs), you could see a pretty substantial pressure in recirculate mode.
Yes, I ran the OCLT a few times after the opening SLAM and it checks out. I really do not think my chemistry is to blame.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,003
Tucson, AZ
The pressure gauge on the Hayward valves are in the pump inlet chamber, so if you have enough restriction in the return path (small eyeballs), you could see a pretty substantial pressure in recirculate mode.
Interesting. I had not considered that for the top mount valves the gauge might still be getting pressure depending on its location. For the side mount valve, where the gauge is on the top the filter, there is 0 reading on recirculate mode.

Given that info, I now too suspect that the filter is doing its job and capturing something in the water.

Have you ever done a Deep Clean of your sand?
 

Joeten30

Member
Jun 22, 2017
14
Boston
Interesting. I had not considered that for the top mount valves the gauge might still be getting pressure depending on its location. For the side mount valve, where the gauge is on the top the filter, there is 0 reading on recirculate mode.

Given that info, I now too suspect that the filter is doing its job and capturing something in the water.

Have you ever done a Deep Clean of your sand?
I have not. What does it entail? Is it just a chemical treatment to the sand?
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,003
Tucson, AZ
Here is the thread that is linked to from Pool School (have you read Pool School yet?)
 
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Joeten30

Member
Jun 22, 2017
14
Boston
Here is the thread that is linked to from Pool School (have you read Pool School yet?)
Interesting!
I have read Pool School in the past. Got basically all of my pool knowledge from it. However, I must have missed the Deep Cleaning part! I'm gonna give this a whirl this weekend.
Thanks!

Another thing I've been noticing, Is after I run the system in recalculation mode for over 20 mins and put it back into Filter mode, the pressure seems to go down 8-10 PSI. Very strange.