Adding DE to a sand filter

[BigDave]

Nope, not personal experience. My answer is based on what I've read here and what I've observed. The sand bed looks (to me) finer than the material used in DE filter grids and fingers and this is the basis for my statement that the DE should coat the top of the sand bed. I would also expect DE to pass right through a sand filter's laterals based on my observation of my filter's laterals and the fineness (for lack of a more accurate term) of DE. So, some repetition and some reckoning - I hope I haven't misled.

I'm sure there's some penetration into the sand bed but I'd be surprised if the DE would be dispersed throughout. Increasing the pump speed and pressure probably did push the DE a little deeper, breaking up the layer that had formed at low speed.

I did use a cellulose DE replacement product last year that gave me no apparent performance boost. I discovered upon inspection at closing that it had clumped into what looked like a newspaper delivered to the driveway before a thunderstorm and driven over several times (this happens often in my driveway).

[AnnaK]

Thanks for the various explanations, guys.