I have a 24ft A/G pool with a Hayward 100lb sand filter have had no problems last several years until yesterday,I put in my auto vacume watched it run. few min and went in the house,about 30 min later I went to check on the progress and found the hose to the vacume had disconnected from the skimmer and the skimmer was running without the basket of course because the vacume was directly placed in it,i also noticed my water had white foam all over the pool,when I shut off the pool pump the water from the pump came back up though the skimmer.i placed the basket back in the skimmer,backwashed,then rinsed and when I shut off the motor the water came back up through the skimmer again and pushed up the basket,my question is how can I stop the water from backing up from the skimmer when I shut of the motor and it is still foaming the water while the filter runs,I guess when the vacume hose disconnected from the skimmer it caused all these problems,if anyone can help I really would appreciate it,also my water levels were all balanced before this happened,thank you!
filter problem,water backing up thru the skimmer
- Thread starter irishrover01
- Start date
Welcome to the forum. 
You have two separate issues. Let's address the water flowing backwards first. If your installation is typical, the pump is below water level, correct? The only way for the water to back up is to have a force pushing it. That source is likely air in your filter that is trapped and compressed when the pump is running and when the pump shuts off the compress air at the top of the filter pushes the water backwards. You have to release the air. Does your filter have an air release valve on top? That should do it.
Now, what's causing that? You are or were sucking air into the pump from your skimmer. If the water in your pool is high enough to keep the skimmer from sucking air, the problem is solved.
Let us know if that fixes it.
You have two separate issues. Let's address the water flowing backwards first. If your installation is typical, the pump is below water level, correct? The only way for the water to back up is to have a force pushing it. That source is likely air in your filter that is trapped and compressed when the pump is running and when the pump shuts off the compress air at the top of the filter pushes the water backwards. You have to release the air. Does your filter have an air release valve on top? That should do it.
Now, what's causing that? You are or were sucking air into the pump from your skimmer. If the water in your pool is high enough to keep the skimmer from sucking air, the problem is solved.
Let us know if that fixes it.
Thank You Dave S., I indeed was getting air into the pump through my small filter that is directly attached to my pump motor,a new o ring did the trick,I do appreciate your response.
Glad it's fixed. If you are still foaming, it is usually associated with using algecide.....something we don't think is necessary.