HELP NEEDED - Pentair manifold pops off stand pipe

[JamesW]

The pressure before the grids should always be higher than or equal to the pressure after the grids.

If the flow is completely blocked downstream of the filter, the pressure before the grids will be the same as the pressure after the grids.

The pressure in the standpipe should never be higher than the pressure in the filter or inside the grids.

Maybe the grids are filling with air and floating up?

 

[HermanTX]

attached a few pictures. One with what it looks like when the manifold pops off, one at the higher prime setting and lastly the lower prime setting I just did before posting this here.

The flow of water is from outside the grid to the inside of the grid then upwards to the manifold then out of the standpipe.
The pressure drop is across the grid - so the higher pressure is on the external of the grid and also pressing down on the manifold while the lower pressure flow inside the grid is pressing up on the manifold. This is the pressure recorded on the pressure gauge and is why as the pressure increases it is due to the grid being dirty causing an even higher pressure drop across the grids i.e., restricting flow to the pool. So, without having all the dimensions, it is predicted that the greater force is exerted to keep the manifold on the standpipe.

In order for it to lift off the standpipe, the pressure inside the manifold had to be greater than that on the outside or have some instantaneous energy that enables the manifold to lift upwards. A leaking oring seal or a crack manifold could allow pressure to be balanced and possibly in that instance push the manifold upwards. Also, should the pump be running, and you switch from backwash to circulation mode there could be an instantaneous surge of pressure.
My guess this is happening directly after you have cleaned the grids and adding DE as that is the point in time where the pressure drop across the grids is the least i.e., before any debris is trapped thus increasing the pressure drop.

I don't have a firm answer, but the design tells me that the manifold should stay on the standpipe unless there is some internal force to push upwards that is greater than the force being exerted to keep it in place. Sorry for the long winded thoughts.

EDIT - I see James has the same thoughts - although his is more concise.

 

[JamesW]

Backwashing can push the grids up and off of the standpipe.

I would not use the backwash setting and instead just take the filter apart and clean it if necessary.

 

[eostrike]

Backwashing can push the grids up and off of the standpipe.

I would not use the backwash setting and instead just take the filter apart and clean it if necessary.

I do not backwash, I clean the filter each time as you mention. This issue only happens after cleaning the filter and turning the pump on. I always have the air valve at the top of the filter open until the water comes out. You can hear the air coming out of the valve like crazy and once the water is about to come out of the valve pop you hear the manifold come off.

I just removed the internal check valve going into the heater as another member mentioned something about deadhead (never heard this term before). The filter drained back into the pool as it should since the plumbing was now open. I then put everything back to the way it was before making changes to the prime setting. I set the prime back to the original 2500 and set it for 1 minute as anything lower is 0. I turned on the pump and right when the water got to the top of the filter I heard the manifold pop off yet again.

This is so frustrating, now I have DE back in my pool but I stopped the pump before it all went back in the pool. Pictures will be below of just moments ago. Don't mind the algae I have been shocking the pool and was going to clean it tomorrow. You will see exactly how the manifold was sitting once I lifted the lid off, not any different than the previous picture on my first post.

After getting the lid back on I turned the prime down from 2500 to 1250 and set the time to 0. I started the pump back up and the manifold did not pop off as I you can hear when it does and see all the DE blowing in the pool. It is so weird it does not do it every time. I do think it has something to do with the priming as when the pump is primed it does not experience this issue.

I am hoping with all the great suggestions/comments here I can get this issue resolved. It does not do it every time but more than it should. It only does this after a filter cleaning as the filter is empty of water.

Here is the fun I keep getting -

 

[JamesW]

I suspect the the grids have air in them and they are floating up as the tank fills with water.

The air bleed in the manifold is not very good and it might be clogged.

I would secure the manifold to the standpipe using some zip ties.

 

[eostrike]

I suspect the the grids have air in them and they are floating up as the tank fills with water.

The air bleed in the manifold is not very good and it might be clogged.

I would secure the manifold to the standpipe using some zip ties.

View attachment 459241

James, thanks for that suggestion. Since I now need to get what DE washed back in the pool out I will not be cleaning the filter tomorrow. I will clean it aft work sometime in the next few days. I have plenty of cable ties and can try this as suggested and I think I will but I would love to get to the bottom of this.

Am I doing it correctly when the pump is priming by keeping the valve at the top completely open until the water blows out or should I keep it closed when priming. Could that be causing the unbalance in pressure?

And then the other question I have here is do I really need to have the prime function on as the pool equipment is maybe 15' away from the deep end. I am mentioning this as some pools have the equipment a good distance away from the pool.

I want to once again say thank to all for their input.

 

[HermanTX]

The zip tie is a good idea. Additionally, before you put the top half on, fill the bottom full of water to an inch below the seal ring. Take note if the grids fill with air or look swollen with air. This should add some weight to the grids as a good 1/3 to 1/2 should be filled with water.

I always leave my air vent open when I kick on the pump after cleaning the DE filter to let the air escape and close it when water begins to spurt out. Not to say that is what causing the issue, but it does not affect my filter. In fact, I have a heck of time getting the manifold off of the standpipe when I open it to remove the grids from the lower body.

 

[JamesW]

Below, you can see your current air relief, which looks clogged.

Try to clean the holes, but don't enlarge them or they will allow DE to pass.

The fabric might not be allowing air to escape for some reason, which might be due to fabric damage from fouling from oils or scale.

Maybe soak the grids in a cleaning solution.

The manifold part that goes onto the standpipe might be too loose.

Zip ties should prevent the grid assembly from popping off.



Below is the old air relief, which was better.

 

[trivetman]

And then the other question I have here is do I really need to have the prime function on as the pool equipment is maybe 15' away from the deep end

The priming function is just running the pump at a high rpm to clear the pipes and pump basket of air. If you are able to clear the air out at a lower rpm such that you don’t have the manifold problem, go for it.

Regardless of the speed you prime at, its probably a good idea to clean out your air vents and grids as well.

 

[HermanTX]

Below is the old air relief, which was better.

Note this comment from the OP on an earlier post - "When this problem occurred years back I purchased a non-Pentair manifold in hopes this issue would stop. Changing to a different brand manifold did not do anything to resolve what was happening with the Pentair manifold."

I do believe that something is not allowing the air to escape properly from INSIDE the grids & manifold which is pushing up the manifold off of the standpipe.

 

[tejas]

Only time I've seen this happen is after cleaning the filter and starting the pump back up with the backwash valve still in backwash mode.

 

[wireform]

I wonder if the close proximity of the pump to the filter and a very short pipe, can this possibly be the root of the problem ?

 

[eostrike]

Below, you can see your current air relief, which looks clogged.

Try to clean the holes, but don't enlarge them or they will allow DE to pass.

The fabric might not be allowing air to escape for some reason, which might be due to fabric damage from fouling from oils or scale.

Maybe soak the grids in a cleaning solution.

The manifold part that goes onto the standpipe might be too loose.

Zip ties should prevent the grid assembly from popping off.

View attachment 459244

Below is the old air relief, which was better.

View attachment 459243

Thank you for your suggestion, I had the original Pentair manifold with the air relief that sticks up and had the same issue. That is why I replaced it with the one did to see if it would fix my problem which it did not.

 

[eostrike]

So this is so depressing.... Today after work I cleaned my filter again as it was time since I was finished with shocking it from a little over a week ago. Turned he pump on, had air relief open and once the water started coming out I closed the valve. I then proceeded to put 6 scoops of DE in the skimmer. Once I got the the 6th one all the DE started blowing back in the pool.

I shut the pump off and took the top of the filter off and once again the manifold had lifted off. I then put it back together and started it up. Waited a few minutes and removed the top again and the manifold was still on, this time there is no DE in the filter as it is now all in the pool. I did this once more and it was still not popped off.

Again I want to say the original Pentair manifold had that issue which is why I purchased a different brand.

Sometimes I can hear the manifold pop off before I even add DE and this time it did not start blowing back in the pool till my 6th scoop.

Pool is now going to run for a few hours this evening to try and pick up as much DE as possible to get it back in the filter.

This is a mystery that I hope can be solved at some point, it has been like this for several years now.

 

[trivetman]

What is the condition of the grids? A few have suggested that the grids themselves may be trapping air and floating. Is the material somehow clogged such that air cannot pass through?

It would be strange for this to be the case but have water flowing just fine….

 

[eostrike]

What is the condition of the grids? A few have suggested that the grids themselves may be trapping air and floating. Is the material somehow clogged such that air cannot pass through?

It would be strange for this to be the case but have water flowing just fine….

Grids look perfectly fine to me but like I mentioned I replaced the manifold I also replaced the grids as well. Not at the same time, when the manifold did not resolve the issue I replaced the grids. The only thing inside the filter that I have not replaced is the stand pipe. I purchased the grids in July 2021.

 

[trivetman]

You got us all stumped!!

 

[Jimrahbe]

eo,

At this point I am not sure why you have put up with this problem for so long or why you even want a DE filter...

I have a large cartridge filter and I open and clean it twice a year. Dirt simple plumbing, no backwash or MPV to go bad or leak, very low backpressure.

I have two rent house pools that have old DE filters, I can hardly wait for them to crack open so I can replace them with large cartridge filters.

I will never ever install a DE filter again.

Thanks,

Jim R.

 

[HermanTX]

Well I am going to throw this unorthodox suggestion out.
mark where the oring on the standpipe sits on inside of your manifold when in full seated position. Then take a Stainless Steel screw and tap on outside of your manifold BELOW the oring seal position. Lightly sand the ID of the manifold to remove any burrs. Reassemble, tap the screw that it pentrates the standpipe. I do not think it will leak but you can add some lube to it to try to help seal. This way your manifold is now fixed to the standpipe. Note - it appears there is not sufficient space above the oring to insert a screw, but you can measure that and need to be precise on your tap.
It does not need to be a massive screw - just large enough to hold the 2 pieces together.

 

[eostrike]

You got us all stumped!!

Me too .