Swimming Pool Backwash Trouble

by Kim
(San Angelo, TX, USA)

I backwashed and water is clear but pressure is still at 20 and won't go down. This is the third year for that sand filter. Will a filter cleaner do the job?

Thanks for your question Kim

What I have normally found with sand filters is when there's high pressure it's either a low sand level or "channeling". This is when there's so much dirt, debris, and oily matter in the sand that the water can't be filtered properly. The water will then go down the sides of the filter, following the path of least resistance, and be returned back to the pool as non-filtered water.

First turn the pump motor off and open the top of the filter. Check the sand level per the owner's manual, then check for channeling. The sand should be smooth all the way around the top. Feel the inside of the filter around the edges for pockets or holes in the sand which should be obvious.

If there are pockets and holes your best bet would be a filter cleaner. A good one that I've found useful is called "Filter Fresh". I use this at the YMCA pool and it works great.

The directions on some cleaners might tell you to pour the cleaner in the skimmer. Unfortunately you don't know how much actually gets into the filter.

A better way is to pour the solution directly into the filter and allow it to sit overnight.

The next day top-off the filter with water, put the top back on the filter, and begin in backwash mode. This will flush out the dirt, oil, and cleaner.

Turn off the pump, take the top off the filter, and check for channeling again. Repeat these steps if necessary.

Thanks for your question and let me know how this works for you.

All the best

Robert