Why is my pump pressure rising when filter is engaged...but there's nothing inside the DE filter?

aharon

Member
Jun 21, 2014
20
Wyndmoor, PA
I'm baffled. My Hayward Superpump and MPV, when set to filter as brand new without adding DE showed a pressure of 10psi. So that's baseline with a water path impeded only by empty grid fabric. Adding DE brought the psi up to maybe 11 or 12. So that's a more useful baseline. Later, I was experiencing higher pressure AFTER backwash, 15 to 17; even after multiple backwash/rinse cycles and clear water, I couldn't get the pressure below 15 psi. So here's the weird part: I removed the filter grids from the filter and closed it up and turned it on. With nothing in the water path, just water coming into the empty filter case and exiting without passing through any media, I'd expect pressure to drop back to 10psi, or at least to drop lower than with installed grids. But STILL stuck at 15psi. There should be no difference now between recirculate and filter except a foot or two of extra travel for the water. Pressure gauge is a year old, fluid-filled, seems to move ok, does drop to zero during recirc or power off, does rise to 20 or so before I backwash. The filter has big inlet and outlet ports, there's no clog I can see. Pump basket is empty, no debris in the impeller and again, nice low pressure without the filter inline which means my pipes should be clear. The only piece that remains an unknown is the MPV, which I hear is tough to take apart and reassemble. Google only offers information about leaking MPVs and replacing gaskets, nothing about clogs. Anyone encountered this before? This problem appeared last year and I just lived with it.
 

cowboycasey

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When it comes down to it if you have water coming out of the returns there is no blockage...

After backwash that is your new low pressure... when it raises 25% backwash again.. DE filters should not be run without DE media in them, it can mess them up..

What I do not know is when to completely take the grids out and clean them.. :)
 
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clambert1273

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Jun 13, 2013
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When it comes down to it if you have water coming out of the returns there is no blockage...

After backwash that is your new low pressure... when it raises 25% backwash again.. DE filters should not be run without DE media in them, it can mess them up..

What I do not know is when to completely take the grids out and clean them.. :)
My old de filter I took grids out for cleaning start of season every year, then added my 6 cups rest was just backwashing and recharge 4 cups
 
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aharon

Member
Jun 21, 2014
20
Wyndmoor, PA
I have new info: filter loaded with new DE and set to filter: 16psi starting.
Filter loaded with new DE and set to rinse: 10psi.
Am I correct in understanding that the only difference between filter and rinse is that from the MPV, Filter sends the water out the return while Rinse sends the same water out the waste line?
If so, this suggests that my Filter problem is somewhere inside or between the MPV and the return outlet. @cowboycasey is it possible that the return has a partial obstruction, like a sturdy leaf or twig that has accumulated more debris? I wish there was a way to measure pressure without the gauge on the filter so I could see if Recirculate showed 10psi, or something higher.
 

cowboycasey

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there is no way anything bigger than 3 microns got past a DE filter... the reason it is 10 psi on rinse is because you have no plumbing like you do back to the pool.. If you had the same exact pipe length with all the elbows on your rinse pipe it would be the same exact pressure...

It really does not matter what the pressure is in filter, just what it is after backwash and backwash again once it reaches 25% more pressure :)
 

aharon

Member
Jun 21, 2014
20
Wyndmoor, PA
No heater or anything else inline. @cowboycasey ok, I see your point about the return being more convoluted than the waste hose....although the waste hose is a lot longer, 50', but it's a straight shot. I just don't understand how the pressure in filter mode is the same whether or not I have grids installed or an empty space (filled with water of course). One final possibility is that there's something caught in the filter MPV channel that got in during a recirculate period, so it would have to make it past the pump basket and impeller but not into the filter. But I don't even know if that's how an MPV works.
 

Saturn94

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Mar 11, 2015
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It’s actually not difficult to open up the MPV to see if anything is stuck in there. Just remove the screws and lift out the top assembly.
 
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