Loosing Sand During Backwash

joronimo

Active member
Jun 4, 2019
27
Phoenix, Az
Hi, I have been noticing sand coming out when I backwash my sand filter but not noticing any in the pool. My vacuum could be catching anything that is going into the pool but I doubt it. If it was entering the pool at the rate is comes out of the backwash I could feel it when filtering at the returns. I put new sand in last November and slightly overfilled it. I pulled the excess out this spring so it could still be too full (I am planning to let it keep washing out and see if it stops at some point).

Does anyone have any thoughts on this?

Thanks!
 

AndyTN

Bronze Supporter
Mar 27, 2019
255
Memphis
How much sand? If you are seeing a few specs go by, then normal and these may not all be sand. Is it happening during backwash or just when you rinse? It is even more normal when if you only see a small amount of sand only during rinse. Backwash pushes water up through the sand which is heavy enough to not get pushed up with the dirt. Rinse is washing on top of the sand and then out which will stir up a few grains off the top of your sand "pile".
 

joronimo

Active member
Jun 4, 2019
27
Phoenix, Az
How much sand? If you are seeing a few specs go by, then normal and these may not all be sand. Is it happening during backwash or just when you rinse? It is even more normal when if you only see a small amount of sand only during rinse. Backwash pushes water up through the sand which is heavy enough to not get pushed up with the dirt. Rinse is washing on top of the sand and then out which will stir up a few grains off the top of your sand "pile".

Its a fair amount, enough to see on the ground. I would say maybe 1/4 cup full or so, depending on how long I backwash. It seems to happen during both backwash and rinse, but more predominantly during backwash. My thought is that it is just overfilled since it doesn't seem to occur during filtering (nothing in pool).
 

AndyTN

Bronze Supporter
Mar 27, 2019
255
Memphis
Its a fair amount, enough to see on the ground. I would say maybe 1/4 cup full or so, depending on how long I backwash. It seems to happen during both backwash and rinse, but more predominantly during backwash. My thought is that it is just overfilled since it doesn't seem to occur during filtering (nothing in pool).
Have you read through this article? I know you have already replaced your sand but it gives a great tutorial about the functionality of a sand filter. The laterals and sand pipe keep the sand from entering the pool so you should only see that when they are broken. How many inches below the multiport is the level of sand? The sand will raise up slightly when water is pushing up from below but I wouldn't think it would raise more than a few inches.

Overfill is likely but you already reduced it once. If you are only backwashing every few weeks, I wouldn't worry too much this year and see if it continues into next year. Your excess should just be pushed out with the ideal level happening on its own.