DE Filter creates geiser thru skimmer when turned off q's

[rio002]

Hi there, new to owning a DE filter but learning as I go. The filter itself is a Spartan (company no longer exists) with Hayward controls so it's an old one. Problem is, when it's run for a couple hours it starts acting like it needs to be backwashed ie: low return pressure, sounds like it's trying to refill the tank etc. but when I shut it off it will belch out the return jet and send a 5-6ft tall geiser out the skimmer, it seems to empty the whole filter tank as I have to then wait for it to refill before it will backwash and rinse. The pressure prior to shutting it off is between 20 and 25psi. I have a 10,000 gallon above ground pool, so it has about 3 lbs. of fresh DE in it and a new seal around the tank. Now if I go right back out within an hour or so and shut it off to backwash and rinse again I don't get the geiser just a small belch out of the skimmer. A few weeks ago it ran fairly normal at 15-20psi and only did this when I knew the DE was low--but right now there is plenty of DE in it and it's still doing this. Any advice will be greatly appreciated. Thanks!

[Poconos]

Sounds like the filter tank has a lot of trapped air that is under pressure. A large volume of pressurized air will cause the geyser effect. Filters should eventually purge themselves of air by some mechanism. Not familiar with DE filters but is there an air relief valve or anything that might resemble one on the top somewhere? If you find something try opening it a little while the pump is running until water comes out. Best guess for now.
Al

[rio002]

There is an air release valve at the top, and I open it when the tank is refilling to let the air out but I'll try opening it before shutting it off and see if that helps. LOL the last geiser sent my skimmer basket flying into the air and it landed dead center of the pool, that was fun to find as the pool isn't cleared up yet

[rio002]

Alright I was just outthere, and opened the valve for a minute before shutting it off, but it still did the geiser thing. Still wondering what's causing it.??

[JohnT]

Somewhere you most likely have air trapped. Any capped off returns or cleaner ports? Solar heating or other heater that hasn't been bled? Long pieces of flexible hose connecting your filter to the returns?

[rio002]

I checked all connections, no leaks, none capped off, all hoses are less than 4ft long except the backwash hose of course. No heater or solar accessories. But it seems to be building up the air up from somewhere over time, just can't find where.

[Poconos]

Something is wrong. If you opened the air release for a minute, that sounds like a long time. Did water finally come out? You need to leave it open until that happens. My guess is it has to be the filter bacause if there was trapped air after it, like in an unused return line or something, it (compressed air) would have to move the mass of water in the filter back through the pump and skimmer and I can't imagine getting that much of a blast from the skimmer. A thought, have someone hold their hand over a return jet as you kill the pump and see if you continue to get a flow for a couple seconds after the pump is shut off. Just another data point. Other than these comments, I'm out of ideas for now.
Al

[PatL34]

Something is wrong. If you opened the air release for a minute, that sounds like a long time. Did water finally come out? You need to leave it open until that happens. My guess is it has to be the filter bacause if there was trapped air after it, like in an unused return line or something, it (compressed air) would have to move the mass of water in the filter back through the pump and skimmer and I can't imagine getting that much of a blast from the skimmer. A thought, have someone hold their hand over a return jet as you kill the pump and see if you continue to get a flow for a couple seconds after the pump is shut off. Just another data point. Other than these comments, I'm out of ideas for now.
Al

Seems to me what is not working is the check valve, or lack of it. A check valve should be installed immediately after the pump, and will prevent your "gieser' very quickly.

This could be bad workmanship on the part of the original installer.

Hope this helps.

Pat

[Poconos]

There should be no need for a check valve in a normal system. Granted it would probably solve this specific problem, but there is some issue that is not yet explained.
Al

[rio002]

OK I went back through and tightened all my hose clamps (was surprised I got a 1/2 turn or so out of the ones on the filter-these were tight 3 weeks ago). I let the filter run all day, it was at 25psi tonight, I opened the air valve and let it stay open for about a minute- the whole time water was coming out with some air too. I left it open til my psi dropped to 20, then simultaneously shut off the pump and pushed the control handle down so it was in between gears--this caused only a small belch out of the skimmer, backwash hose and return valve. It sounded like I got a belch from under the control handle though- is that normal when it's in between gears?
Oh, and the return valve does continue to push after the pump is off for about 10 seconds. I really appreciate all your help in tracking this down, I've only had sand filters before, but those only survive so long lol.