There was a post a few days ago about using DE in a sand filter. I have tried that in the past, but the pool was so cloudy I had to backwash about twice a day and it didn't seem to do much good because the flow would drop to almost nothing before backwashing so I quit. After reading the thread and seeing where people claimed a big improvement I thought I would try again. My pool water has been clear as glass for months, but I thought maybe the DE would improve the appearance even more.
The day before yesterday I added 2-1/2 cups of DE to get a 1 lb pressure increase across the filter. I turned off the pump timer and let it run around the clock. Yesterday the water was clear, but I could not tell any real difference. The filter pressure had not increased at all - so-far-so good. The pump ran all day and all night and today the pool still looked about the same as always and the filter pressure was still where it was when I started.
This afternoon I decided to skim some leaves off the surface and was walking around the pool and came to the shallow end directly across from one of the returns and when I looked down the bottom was a nice pure white - WHAT IS THAT? My first thought was the liner had been bleached out, but I got out the pool brush and brushed the bottom and a nice pure white cloud came up. OH **** - it looks like some of the DE got though the filter and settled out on the bottom. I started brushing in a few more places and everywhere I brushed a white cloud appeared - no wonder the pressure had not increased all the DE went though the filter into the pool.
I'm reasoning the only way that could happen is if some of the inlet water is short circuiting the filter and going straight to the outlet. That must mean the multi-port valve gasket is bad and I just happen to have a spare. I've learned that the gasket should be replaced and the spring and stem assembly lubed up about once a year. So I remove the top of the valve and start to scrape the old gasket out, but think to myself I better wait and make sure I can find the spare first. Well I find the spare, but guess what - it's the wrong gasket and will not fit my valve. So I'll have to make another trip to the pool store tomorrow and listen to everything I'm doing wrong in caring for the pool from a 19 year old high school drop out. I hate going in that place. I don't want to be rude, but it's all I can do to keep my mouth shut.
Now I'm going to have a heck of a time getting all the DE out. Guess all I can do is vacuum the entire pool and hope it stays in the filter this time.