I have had my Intex 16 inch sand filter for one full season and the beginning of this season. I noticed a problem last year but didn't troubleshoot it until this year.
The problem is that the sand loads up with debris from the pool but gets trapped behind the "pre-filter disk" during backwashing.
There is a plastic disk shaped cup located just under the multi-port valve. Hayward calls it a diffuser. Intex does not sell this part separate from the valve so I don't know what they call it. It has very thin slits that restrict large particles from entering the sand filter. It is very flimsy and is held on by two screws about halfway out from the center of the disk. I noticed right away that the plastic shows clear signs of deformation while under forward water flow. This flow causes the plastic to flex away from the surface of the multi-port valve and allows large particles to flow around the cup and into the sand. During backwash the disk flexes back upward and against the multi-port valve which seals off the large opening. During the backwash all the large debris collects on the disk and reduces flow to very low rates. This makes the backwash very ineffective. The only way to clear the debris is to open the sand filter and was the sand manually. Which I have been doing on a regular basis.
I now use a skimmer sock to reduce the large particles and I vacuum to waste when I have large debris in the pool.
I decided to re-engineer the disk today. I drilled 4 large holes to the sides of the disk to allow better backwashing. The holds are at the uprights of the cup. I was hoping that the sand would not get through these holes during backwash. I looked at the Hayward design and it has very large holes so I didn't think it would be a problem. As you can expect, lots of sand came out during the backwash. So now I suspect that the disk is meant to keep sand in the filter during the backwash.
I restricted the backwash flow by closing off the skimmer side of the pump during backwash and that worked very well. I think the pump is way over sized for the sand filter. I plan on building a cap with a hole to cover the skimmer port during backwash.
Secondly, I plan on continuing to do full flow backwashing while capturing the escaped sand. My idea is that eventually the sand level will get so low that it will stop getting expelled. If the level is not too low I might try that for a while.
When all this fails I will by a Hayward filter.
Cheers
The problem is that the sand loads up with debris from the pool but gets trapped behind the "pre-filter disk" during backwashing.
There is a plastic disk shaped cup located just under the multi-port valve. Hayward calls it a diffuser. Intex does not sell this part separate from the valve so I don't know what they call it. It has very thin slits that restrict large particles from entering the sand filter. It is very flimsy and is held on by two screws about halfway out from the center of the disk. I noticed right away that the plastic shows clear signs of deformation while under forward water flow. This flow causes the plastic to flex away from the surface of the multi-port valve and allows large particles to flow around the cup and into the sand. During backwash the disk flexes back upward and against the multi-port valve which seals off the large opening. During the backwash all the large debris collects on the disk and reduces flow to very low rates. This makes the backwash very ineffective. The only way to clear the debris is to open the sand filter and was the sand manually. Which I have been doing on a regular basis.
I now use a skimmer sock to reduce the large particles and I vacuum to waste when I have large debris in the pool.
I decided to re-engineer the disk today. I drilled 4 large holes to the sides of the disk to allow better backwashing. The holds are at the uprights of the cup. I was hoping that the sand would not get through these holes during backwash. I looked at the Hayward design and it has very large holes so I didn't think it would be a problem. As you can expect, lots of sand came out during the backwash. So now I suspect that the disk is meant to keep sand in the filter during the backwash.
I restricted the backwash flow by closing off the skimmer side of the pump during backwash and that worked very well. I think the pump is way over sized for the sand filter. I plan on building a cap with a hole to cover the skimmer port during backwash.
Secondly, I plan on continuing to do full flow backwashing while capturing the escaped sand. My idea is that eventually the sand level will get so low that it will stop getting expelled. If the level is not too low I might try that for a while.
When all this fails I will by a Hayward filter.
Cheers
Let us know how it end up!