Check valve keeps failing due to back pressure?

atom519

Member
Apr 28, 2014
17
Kansas City, KS
We put in a heater a few years ago, and have a reoccurring issue with the check valve - which is connected on the return line from the heater - causing a leak and/or bursting leaking water everywhere. The first time it happened was at the very end of the season last year, and again this year at the end of the summer. We opened the pool in May and ran for ~4 months with no issue. Kind of strange. Both times it resulted in that return line plumbing getting very hot coming out of the heater. We just replaced the liner this spring and added an additional return straight from the heater to help alleviate any bottlenecks flowing back into the pool.

I'm thinking it might be related to the backpressure issue I've been having lately, when I shut off the pump it releases a ton of pressure/water back through the suction side/skimmer. Not sure what is causing it, might be a slight leak in the basket gasket but it looks solid. The check valve itself is a cheap 1.5" PVC spring check style you can get from big box stores, I'm wondering if the back pressure is somehow too much for it and making it come apart at the seams. It's threaded in the middle, and after it gets ruined I can twist it but it slips and never gets fully tight. I try and backwash regularly, doesn't seem to matter regarding the back pressure.

I guess my question is, has anyone had a similar experience with check valves getting ruined? I'm thinking I should get a proper swing-style check valve to replace (better GPM flow), and should probably put another one on the suction line in front of the basket, but I'm a little concerned with where that back pressure will go (filter?) if not allowed to release into the skimmer. Also considered just removing the check valve entirely from the return line on the heater - but sounds like might not be a good idea.

I know a diagram would help here, hoping to update but posting from work atm.

10k gallon pool
sand filter
vinyl liner
Jacuzzi 266k BTU heater
Hayward 1.5hp pump
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
23,106
Bedford, TX
519,

I doubt it is back pressure, most likely the check valve is just too close to the heater...

Show us a couple of pics...

Thanks,

Jim R.
 

atom519

Member
Apr 28, 2014
17
Kansas City, KS
See attached. Check valve is ~18" away from heater but I'm not certain best practice here. I just replaced it and so far it's running without issue but the more I play with the spring the more I think it's inhibiting water flow and I'm best off replacing (likely further way) with a proper flap style check valve.

The rest of the plumbing should be mostly obvious, I'm more than open to any ideas for simple improvements for dealing with back pressure. Thanks in advance folks.
 

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Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
23,106
Bedford, TX
519,

I don't see a Tab Feeder in your set up... Do you have one I can't see? If not, you can just take the check valve out all together..

The whole purpose of the check valve is to prevent very acidic water, that is inside a tab feeder, from flowing back into the heater when the pump is off.. The acidic water can quickly eat the inside of a heater.. If you don't have a tab feeder, you don't need the check valve.

The main cause of back pressure is the heater itself...

How do you currently chlorinate you pool?

Thanks,

Jim R.
 

atom519

Member
Apr 28, 2014
17
Kansas City, KS
519,

I don't see a Tab Feeder in your set up... Do you have one I can't see? If not, you can just take the check valve out all together..

The whole purpose of the check valve is to prevent very acidic water, that is inside a tab feeder, from flowing back into the heater when the pump is off.. The acidic water can quickly eat the inside of a heater.. If you don't have a tab feeder, you don't need the check valve.

The main cause of back pressure is the heater itself...

How do you currently chlorinate you pool?

Thanks,

Jim R.
No tab chlorinator, I used to have one and it leaked always so I removed it. Plus only had tri-chlor pucks so seemed kinda worthless. I use bleach for sanitizer with the occasional cal-hypo shock solution when in a pinch.

Curious what you mean by the heater being the source of the back pressure?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
23,106
Bedford, TX
519,

Heaters are notorious for being hard to push water through.. Well, compared to no heater..

As an example... My pool pump runs at 1200 RPM and at that speed I get plenty of flow to turn on my SWCG... Other people with my same pump and SWCG, but with a heater, have to run their pumps at 1500 to 1800 RPM to get the same flow... This is just because the water has to pass through the heat exchanger.. Kind of like putting your thumb on the end of a garden hose, the pressure goes up, the flow goes down.

What are you calling "back pressure"?

Thanks,

Jim R.
 

atom519

Member
Apr 28, 2014
17
Kansas City, KS
519,

Heaters are notorious for being hard to push water through.. Well, compared to no heater..

As an example... My pool pump runs at 1200 RPM and at that speed I get plenty of flow to turn on my SWCG... Other people with my same pump and SWCG, but with a heater, have to run their pumps at 1500 to 1800 RPM to get the same flow... This is just because the water has to pass through the heat exchanger.. Kind of like putting your thumb on the end of a garden hose, the pressure goes up, the flow goes down.

What are you calling "back pressure"?

Thanks,

Jim R.
When I say back pressure I mean it will blow the lid off the skimmer when I shut off the pump if ran for more than a few hours. The strange thing is it doesn't happen every time, just 90% of the time when I shut it off. Kinda weird.

The heater being a bottleneck makes sense I guess. I feel like I had this same issue prior to getting a heater but honestly my memory is so bad so I can't say for certain.

Wanted to say thanks again for the feedback and quick replies, such a great community here.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
23,106
Bedford, TX
519,

The reason your skimmer lid blows off is that you have a suction side air leak.. This allows air to get into your filter, where there should only be water.. Air can be compressed, so it just builds up pressure in the filter until you turn off the pump. It then pushes the water backward and into your skimmer. And wham.. the water shoots up out of the skimmer pipe and blows the lid off the skimmer.

The first place I would look is the pump O-Ring that is not a "ring".. When I had the same pump, I always had a hard time getting a good seal. I'd inspect the seal and lube it with pool lube.

Do you get a lot of bubbles under you pump lid??

Thanks,

Jim R.
 

atom519

Member
Apr 28, 2014
17
Kansas City, KS
I used to get a lot of bubbles under the pump lid, but after we replaced the section line and skimmer it's very minimal. I actually have the replacement gasket, just haven't installed it yet as the current one looks to still be in good shape.

Thanks for the help.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
23,106
Bedford, TX
519,

Well, you are still sucking air from somewhere as that is about the only thing that I know of that can blow the lid off the skimmer.

Let's see what @JamesW has to say...

Thanks,

Jim R.
 

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JamesW

TFP Expert
Mar 2, 2011
28,235
When I say back pressure I mean it will blow the lid off the skimmer when I shut off the pump if ran for more than a few hours.
Due to air buildup.
I used to get a lot of bubbles under the pump lid, but after we replaced the section line and skimmer it's very minimal.
Even a "minimal" amount will eventually create enough compressed air to be a problem.

You have to get to zero air.

You can put a Jandy style check valve between the pump and filter to prevent backflow, but you really need to address the suction side air leak.

You don't need a check valve after the heater. So, I would just remove it.

What is the model or part number of the check valve?

What is the normal filter pressure?

What is the pump model number?

I would make sure that the heater has a 5 to 10 minute cooldown period before the pump shuts off.
 
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