Quote Originally Posted by CarlD
If your pool is clear, your FC and CC are fine, you don't keep having drastic chlorine drops, then the detritus in your filter is past rotting and you needn't worry about it.
Backwash when the pressure goes up. If it's once a week or once a month, so be it.

However, if you DO get an infested sand filter (very rare, but I know someone who had one) it's cheaper and easier to just replace the sand. At $5 for 50 # it's not pricey.

Carl
I'm not sure the idea that the stuff in the filter is past rotting is valid. Last summer I got a new DE filter. The dealer did not supply the multiport valve so I could not backwash. The instructions, as usual said to backwash after noting a pressure rise. After 2 month my pressure only went up 1 1/2 lbs so according to the bood, it didn't need a backwash. But I decided to open it up and hose it off anyway.

I was astonished at the amount of cr@p on the DE. The smell was horrendous. The pool water still showed negligable CC and the FC was held pretty steady at about 5 PPM so it looked OK externally.
But inside YEAUKKKKK.

Next cycle I opened it up again after 1 month. Virutually the same mess. The chlorine does not really break down the stuff in the filter the way I expected it to. Now I clean the filter every two weeks. The blankety blank dealer still has not send the backwash vales so I still do it the hard way. But I won't every leave it for a month or two.

Try taking a 5 gallon pail and catch some of the backwash water about a minute after the flow is reversed. Pretty disgusting.