I have an older used sand filter, and a new pump hooked up to my above ground pool. We are just setting this up and cannot get it to backwash. We replaced the sand thinking that might be the problem. No luck. It has a plunger type handle at the top that says "pull out to backwash and run for at least 2 minutes". When we pull it out and then start the pump it acts as it it sucks the water back up the waste hose for a second then nothing. If we then shut it off and push it back in and restart the pump, it circulates the water just fine, we can see it go into the pump and then into the pool. Does anyone have an idea what is going wrong here? Please help me get this going before it is 90 degrees outside

Well, I guess I made it through the hot weather but, I still need HELP! I have the pool filtering now. It will need to be backwashed at some point and it needs vacuuming right now. Can someone please offer a thought or two on this problem?? Thank you so much! :confused:

I have had the plunger in my backwash unit fail in the past. You should probably undo the screws that hold the plunging assembly in the backwash valve assembly and try to completely remove the plunger (with the pump(s) off) for inspection. It is possible that a part of the plunger broke off, or an o-ring has come out of its grove in the plunger and is preventing the plunger from its full range of motion.

Derek

Thank you, I have taken the WHOLE thing apart and checked it all! It seems as if it is sucking air from somewhere. I took the backwash hose off and blocked that with some plastic and the pump ran much better... better water flow. But the backwash still doesn't work when you pull the plunger out. It comes out about 3" , and no water flow to anywhere. I'm thinking I need to replace the o rings on the plunger though they seem in really good shape and fit tight.? I'm not sure where to go from here.

If the pumps seem to be sucking air when the backwash valve is in the standard non-backwash (running) position, and plugging the input into the valve seems to have reduced an amount of air being sucked into the system, I would have to conclude that the valve (which has a vacuum force against it when the valve is in running position) is leaking. If the o-rings seem undamaged, you might want to lubricate them thoroughly with silicon.

The valve may be leaking because your filter is so clogged that the pumps are sucking from wherever it can. Have you taken the filter apart and examined everything? I would suggest taking a look and also talking to the filter company (or finding the manual) with regard to proper filter maintenance. I do not have a sand filter, but rather a DE filter, and I take mine apart and clean everything once a year. A sand filter is engineered quite differently, but I'm sure that a long period where the backwash is not working would be caused by or at least lead to it becoming completely clogged inside.

You may also have a bad seal between the filter housings that is also allowing air into the system.

Derek