Bad Water Comes Back into Pool When I Vacuum

by Sara Stretch
(Alpha, NJ U.S.,)

I have a Hayward E-series pool filter. When I vacuum my pool, the bad stuff comes right back in through the jet.

I replaced the sand in the filter, and I didn't see anything wrong with the laterals either.

What could be the problem?

Hi Sara.

Sand filters clean dirt particles down to about 60 microns, anything smaller than that will blow right through. Some types of algae will do just that, they will blow right through a sand filter and back into the pool.

You need to remove the algae from the pool by using an algaecide or a shock treatment. Once the algae has been treated it's best to vacuum it out in the waist position on the filter. This gets it out of the pool, not to return.

If you are not sure what to treat the water with you might be better off taking a water sample to a few different pool stores and get their opinions. I recommend a few different opinions because pool stores love to sell chemicals and some will try to sell you a lot more than you need.