Tested DE filter without any grids inside....same high-pressure problem

[aharon]

A new twist for me in year 10 of my pool adventure. My Hayward 24sqft DE filter started up this summer at 10psi base pressure, and gradually crept up to 15psi starting pressure as I've been filtering my pea-soup pool water this past few weeks. Not terribly unusual for my backwash habits mid-season. I then started experiencing a rapid rise in pressure, with it taking only about 20 minutes for it to go from 15 to 20psi or so, with a visible stoppage of flow at the skimmer. With each backwash, I observed the wastewater turn mostly clear, reloaded 2/3 a charge of DE, and started up at 15psi for another 20 minutes until I had to backwash again. I've has summer startups where I've had to do this kind of frequent backwash.
Here's the difference: after removing the grids twice and spraying them off twice (and finding no caked-up DE), and wondering if there was some kind of oil or other goop on the fabric that I could neither see nor feel, I reassembled the filter with no grids inside at all, so the water path is unhindered entering or exiting the filter, and....15psi.
What would cause a raising of pressure 5psi above empty start? I dug around and saw suggestions that somehow debris might be blocking my return line, and that's not impossible because I was at one point recirculating the water full of needles. How can I blow out the return line, when it is sealed to my multiport valve? Are there other causes I should consider?
It's possible my problem is compound, BOTH high starting pressure PLUS a high particle load so my DE gets clogged sooner. The second problem doesn't worry me, but the first does.

 

[ajw22]

You have some restriction causing the higher pressure which you figured out.

Best way we can help you is by seeing pics of your pool, equipment and valves to understand your situation.

 

[aharon]

Her are some pics. First the pool water is mostly opaque, milky with a touch of green, after I superchlorinated it. Previously it was pea soup.


Here are my skimmer and bottom drain lines, with the orange valves, joining and entering the Hayward superpump, then to my MPV and Hayward DE filter.


Out of the MPV comes the single return. At the pool, the return is not covered by a nozzle and jets straight out. To my hand, that water pressure feels normal.



Here is my filter grid assembly, almost all of the DE rinsed off. After drying overnight, I rinsed this residual powder.


Back in we go, ring could use some more sealant but does not leak.

Power on at filter position and pressure is about 14 while I run and dump in 3 lbs of DE, full load.


DE brings pressure up to 15. Air is bled from filter.


After 18 minutes pressure is at 20.



I would think that maybe that brand new pressure gauge is faulty, but when it reads red, I check the skimmer and flow has indeed almost stopped from pressure. So maybe I am really clogging up my DE every 18 minutes? Is 15psi a reasonable starting pressure for an entirely empty filter chamber?

 

[ajw22]

You have algae. Clear your algae problem and your filter problem will likely fix itself.

Confirm the gauge goes to 0 when the pump is off.

Post your water chemistry or update your PoolMath log...

FC
CC
pH
TA
CH
CYA

Do a Overnight Chlorine Loss Test

How do you chlorinate the pool?

 

[aharon]

I do have algae, which I manage every year with liquid chlorine according to the recommendations and methods of this site. FC has ranged from 20 to 8. I haven't tested any other water paramemeters while working on the algae. What is different is that my filter shows high pressure even without filter grids to slow the water down. If the pump is off, the pressure reads zero. When I have newly cleaned grids and a fresh charge of DE, the filter reads 15psi, which is high for this filter in that cleaned condition. But when I remove the grids so that the water path is unobstructed, the pressure is still 15psi. It should at least read 10psi like it used to in previous years, unless my pressure gauge is faulty.

 

[ajw22]

Is it a new gauge?

 

[aharon]

It is a new fluid-filled gauge. It rests at zero and seems to move well. I thought it might be failing, but there is a match between when the gauge enters the red zone at 20psi, and when the suction at the skimmer has stopped. It seems to be reflecting reality like my old Hayward gauge.
Do MPVs ever get clogged with debris inside, or do clogs just not happen there with all the reversals of pressurized flow?

 

[ajw22]

I think clogs can happen anyplace.