I am in the process of having masonry work done around the pool and have a lot of fine silt in the pool which I am trying to clean up. I have noticed that some of the fine silt is passing through my DE filter. The filter was brand new last year and the pool was closed by the pool builder. I am assuming that he backwashed the filter as part of the closing. Since I did not have time to open the filter and do a thorough cleaning, I added 3 pounds of DE (filter is rated for 5 pounds). Could I not have enough DE in the filter which is causing the silt to pass through? Will a DE filter typically catch fine silt?
DE Filter and Fine Silt
- Thread starter poolneophyte
- Start date
There is silt fine enough to go through a DE filter, but it is rare. Silt that can get through the filter would just look like cloudy water. If you can see individual grains of silt then it shouldn't be able to get through the filter.
Thanks Jason. Based upon your response, I'm assuming that I did not put enough DE in the filter. I am goint to open it up and do a thorough cleaning. I can then add the listed amount of DE powder and know that I have the correct amount.
This weekend, I opened up the DE filter to remove and clean the grids. Being the first time that I have done this, I'm surprised at how easy it was. The parts in the Jandy DEV filter are well labeled and easy to disassemble/reassemble. There are seven longer grids and one shorter grid. The top and bottom spacers clearly label where the shorter grid is installed.
After I cleaned and reassembled the filter I then coated the grids with the initial startup quantity of DE. The fine silt that I mentioned at the top of this post no longer passes through the filter. I have therefore concluded that I did not use enough DE on the initial startup. Without knowing how much DE is lost in a backwash, it seems better to do a complete cleaning and then coat the grids with the initial startup quantity of DE. If I do perform a backwash, how do I know how much DE to use?
After I cleaned and reassembled the filter I then coated the grids with the initial startup quantity of DE. The fine silt that I mentioned at the top of this post no longer passes through the filter. I have therefore concluded that I did not use enough DE on the initial startup. Without knowing how much DE is lost in a backwash, it seems better to do a complete cleaning and then coat the grids with the initial startup quantity of DE. If I do perform a backwash, how do I know how much DE to use?
poolneophyte said:
From what I have read on here, when you do a backwash you do not get rid of all the DE. I have found on here to add about 80% of what it actually calls for. Hope this will help.
I read the manual for your filter and it says (in a round-about way) to add the same amount after a backwash as the initial charge. That seems odd to me. I'd probably go with the 80% rule and open it up at the end of the year and see if there's much left in it.
I just re-read the Pool Filter Comparison in Pool School in which Jason questions whether DE filters should be backwashed at all. If I understand him correctly, his opinion is to open up the filter each time rather than perform a backwash. Based upon how easy it was to do, I am inclined to open it up twice a season and do a complete cleaning. That way, there is no guessing how much DE is required.