This is a bad idea. Diatomaceous earth (de) will go right through a sand filter. It will end up back in the pool and then it is almost impossible to get out. Sand goes in sand filters, de goes in de filters.
Yes. It will clog the filter.
how do you clean jacuzzi sand filter, and replace sand
distinguish between slow and rapid sand filter
Nothing if its a sand filter However if sand is coming into the pool from the filter then you may have to replace one ore more laterals in the sand filter as they have worn and are letting sand through to the pool,
Possibly you are in need of new sand or you can go to the pool shop and ask if they have a chemical sand cleaner.
Do you mean how do you install a sand filter?.
It depends on what you mean by low. You need to check your filter's manual, and see what level it SHOULD be. Lower than that, usually means you are losing sand into the pool (you'll know!) or when you backwash (because the pump is too big for the filter.) If you are losing sand, you need to correct the cause and then add more sand, after you've resolved the problem.
look at the filter if theres a hole well there you go that's the sign
differentiate between slow and rapid sand filters
You just need to use filter paper. use the filter paper than just pour the water and sand on the filter paper. the sand will go to the filter paper while the water will go straight to the beaker or anything below it. That is how you separate it. To separate sand and water you could pour the mixture through a filter. The water would pass through the filter but the sand would remain on top of the filter. If you didn't need to save the water you could evaporate the water and leave the dry sand behind. Or allow the sand to settle and carefully pour off the water first. Then allow the remaining water to evaporate.
If you have a sand filter the laterals in it may be starting to show signs of wear these wil blow sand from the sand filter into the pool when they wear out.