Filter sucking itself in!

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
21,989
Laughlin, NV
Yes there is one between heater and filter.
OK -- So when the pump shuts off, that check valve is a closed at the highest point of the system. That creates a vacuum on he filter side. Like JamesW, I am surprised it is enough to create your issue.

I would consider moving that check valve. Most likely to before the pump inlet. Others can check me on that.
 

frank411

Member
Mar 14, 2016
16
GA
OK -- So when the pump shuts off, that check valve is a closed at the highest point of the system. That creates a vacuum on he filter side. Like JamesW, I am surprised it is enough to create your issue.

I would consider moving that check valve. Most likely to before the pump inlet. Others can check me on that.
I was under the impression the check valve was needed to keep the salt/chlorine from going back into the heater.

Also this happened the first time right after build. Which was before the heater/check valve was installed. Heater check valve installed 2 months ago.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
3,665
Damascus, MD
You can open up the check valve if it is the Jandy style and remove the "guts" which will just make it a pass-through for water. If you are going to do any cutting you could always add in a vacuum/pressure gauge combo after the filter just to see what is going on.
 

PoolGate

Gold Supporter
TFP Guide
Jun 7, 2017
3,665
Damascus, MD
I was under the impression the check valve was needed to keep the salt/chlorine from going back into the heater.

Also this happened the first time right after build. Which was before the heater/check valve was installed. Heater check valve installed 2 months ago.
You don't really need a check valve with a SWCG since when it is off, it does not produce chlorine and when it is on, the chlorine it produces flow into the pool. Check valves to keep heaters isolated from chlorine are needed with the puck feeders. Can you show a larger picture of all of your equipment?
 

markayash

Gold Supporter
Mar 21, 2016
549
Marrietta Ga
Silly question but is there anyway they connected the filter before the pump? I dont know enough about the valves to know of thats even possible but might explain the vacuum?
 

JamesW

TFP Expert
Mar 2, 2011
16,059
It looks like there's a check valve on the suction. A check valve on the return wouldn't make any difference because the water has to flow towards the pool. So, check valves would not help.

The instructions for installation don't say not to put the filter above the pool. So, it should be covered under warranty.

I would not accept a replacement since it has happened twice. That indicates that it's a design issue and not specific to an individual filter.
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,529
SouthWest Alabama
That's a thermoplastic filter body,s so it's pretty flimsy, but I'm surprised like the rest that it collapsed. However I can see it happening under the right circumstances.

Having said that, given the manufacture of the vessel, I wouldn't be afraid to run the pump. Be aware that it's likely to resume original shape when you start the pump, but don't be alarmed by that.
 

JamesW

TFP Expert
Mar 2, 2011
16,059
I would be concerned about excessive structural fatigue with the daily flexing.

If you install a vacuum breaker, that should fix the problem.
 

SPenfold

Well-known member
Aug 20, 2018
53
LI, NY
Could this be a problem with the MPV? How is the quality of your water? Is the filter catching debris? When was the last time you backwashed?
 

JamesW

TFP Expert
Mar 2, 2011
16,059
Most likely, it's just too much suction for the filter. The temperature of the tank will make the plastic more pliable.

A good quality vacuum breaker should solve the problem. It holds against pressure but will open when there is suction.
 

tstex

Silver Supporter
Aug 28, 2012
1,663
Houston, TX
It seems that w the heat temps in excess of 90, and when the pump is off and the filter positioned higher than the pool, the water being pulled back down to the pool is causing the vacuum to suck the water down and cave in the filter I would also check the inbound side of the filter is clogged or has debris that is actually acting like a check-valve. Once the pump comes back on, it reduces the suction by pushing the water through thus pushing out the filter while the pump is running; opposite while the pump goes off..the excessive heat could be exacerbating the matter...
 

frank411

Member
Mar 14, 2016
16
GA
Ok so I just got the courage to turn it back on lol. And it returned to original shape. Yay I guess? Pentair so far giving me the run around. Builder wants no part in it. What to do now? See more pics attached.
 

JamesW

TFP Expert
Mar 2, 2011
16,059
Put a T on the return and reduce to 1/2" and screw in a vacuum breaker like this.

 
Last edited:

frank411

Member
Mar 14, 2016
16
GA
Thanks for your help. I am researching the vacuum breaker thing. i ran it overnight and it shut off around 4am and the caving In did not happen this time. Definitely appears to also be heat related. Did a backwash this morning, but gauge only went from 20 to 10 psi after backwash and pump turned off.

2 Dumb questions.

How do I change the air pressure gauge? It looks to me like its glued on. Unscrewing and remove glue shouldn't be a big deal right? It won't break anything?

How do I bleed excess air from this sd80 tank? I don't think it has a place. In that case what to do. would turning the multiport to backwash suffice?
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,529
SouthWest Alabama
The pressure gauge just unscrews from the multiport. It's probably pipe paste on the threads.

There should be a thumbscrew on the opposite side from the gauge on the multiport to bleed the air off. Be careful when unscrewing it as it will wet you. :)
 

JamesW

TFP Expert
Mar 2, 2011
16,059
I would install a 1.5" T on the horizontal pipe from the pump to the filter with the hole pointing up. Then, glue in a 1.5" slip x 1/2" female thread reducer bushing. Then, screw in the vacuum breaker.

The check valve in front of the pump should keep the pump from losing prime.

You could add an additional check valve on the line between the pump and the filter before the vacuum breaker to help ensure that the pump does not lose prime.