DE filter manifold

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DE filter manifold

Postby ralphdavis01 » Thu 28 Jul, 2011 15:04

The manifold, where the top air bleed fits, keeps breaking? I have a Pentair FNS Plus Vertical Grid DE filter 60 sq ft. a 1.5 horsepower pump, flow is 125 gal/min max pressure is 50 psi which was replaced last fall and have had 2 manifolds break since.

TSH Tech

DE filter manifold

Postby TSH Tech » Fri 29 Jul, 2011 01:18

Yep, that 1.5hp pump will just crush DE grids in no time.

A few things to remember about your setup, you have a very powerful pump, which I assume(??) is pushing water up to a solar system. Maybe, maybe not. The moment those grids get dirty from suntan oils, dirt, leaf oils, water is going to push its way out to the weakest point, such as broken manifolds and those poor little air bleeders don't stand a chance.

Here's the lowdown; I suspect you're letting the filter load up in too long of a time frame before cleaning.
I would guess your filter is running at 23-26 psi when cleaned(brand new DE and cleaned grids), with solars on, if you have them, that goes up to near 30psi. And when dirty, I'd imagine that shoots up to 35psi or over. If you're letting get to 50 psi, it's a no wonder you're breaking equipment!

Herein lies the problem, that filter should be cleaned when it reaches 30psi with no solars on.
With solars on, 35psi is a dirty filter and should be cleaned. Anything over 35psi is the road to breaking equipment. If you have a backwash valve, you can alleviate some of the pressure by letting some of of the soiled filters rinse out. But if the pressure is rapidly climbing back up within a few days, then it's time to tear down the filter and clean the filter grids with a spray cartridge/grid cleaner.

DE filter manifold

Postby ralphdavis01 » Sat 20 Aug, 2011 10:49

Thanks TSH - sorry it's been so long, been working with a local pool servoce store to try and address this problem. They haven't come up with any answers. Checked with Pentair and they were less concerned about the HP of the pump than the throughput of the pump - rated at 75-85 gpm. Filter is supposed to handle up to 120 gpm. However I think you have identified the actual problem based on the history of this problem.

Last fall when the tech was here replacing the pump he told me that when I was vacuuming the pool I should select the "Waste" option on the multi port valve intead of the "Filter" selection. I told him I had no waste line rather a Separation tank. I've had the pool 16 years and never did it that way. He assured me that didn't matter, so the next time I started to vacuum I set the valve to waste (and adjusted other valves appropriately). As you've probably already guessed, that distored my separation tank. When I tried a backwash, a load of DE was pumped into the pool. I didn't know until later that the incident had also ruined the top manifold which caused even more DE to go into the pool.

I had the service vacuum the pool with their equipment which went to waste but that wasn't sufficient. To make a long story short. With the input of your comments, I think what has happened is that the remaining DE in suspension quickly builds up in the filter, the pressure goes up quickly and the manifold breaks. I've gotten as much of the DE out of the pool as I can manually but there is still a lot in there. Is there anything you suggest I do short of draining and cleaning the pool?
TSH Tech

DE filter manifold

Postby TSH Tech » Sat 20 Aug, 2011 19:09

Draining the pool is the absolute last resort. If a pool service can use a portable vacuum setup to vacuum out the remaining DE at the bottom of the pool, that way you are no using your pool equipment to recreate the problem.

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