Sand filter question

[PoolDoc]

1. Is the OFF pressure different than the ON pressure? (If not, you probably need a new gauge.) What is the ON pressure?

2. What HP pump? What size piping? (1.5" or 2")

Not sure about the Start / Clean marks -- I'm pretty skeptical about those. Normally, you should note your 'clean' ON pressure, and then backwash after you see a 4 - 6 psi increase. But, the initial ('clean' ON) pressure will vary from pool to pool depending on piping, filter, and layout.

[dubbedout]

1. The off pressure is at 0psi and when its running its at 16psi and never really rises. I replaced this gauge towards the end of last season so should be fine.

2. The pump is a Magnetek Century Centurion 1.5HP. The piping is 2" that goes into the pump and the backwash piping is 1.5".

Thanks.

[PoolDoc]

Buy the smallest quantity of DE powder you can; add a quart full to the skimmer with the pump on. If you see the DE shoot back into the pool via the returns . . . your filter needs work; dirt is bypassing the sand (or maybe, there's not enough sand). If the DE does NOT shoot back into the pool, your filter is probably functioning correctly, however the DE will cause it to build up pressure more quickly, until you backwash.

Generally speaking, if you have a correctly functioning sand filter, you should backwash only when you need to (4 - 6 psi increase) or 1x per season, which ever comes first.

[dubbedout]

Believe it or not I went and picked up some DE today because my pool has been cloudy since opening it up a couple weeks ago. I read this post today and figured I'd give it a shot. Unfortunately I picked up a 25lbs bag at home depot today, not realizing it only called for 1/3 cup. Anyways, I added the 1/3 cup a few hours ago and did not notice any of it coming out of the returns and my PSI did raise 1 PSI as described in that post.

[PoolDoc]

Sounds like your filter is fine -- just noted your location in a really dry area of AZ. It's entirely possible that, with a low bather load, you could go a season without backwashing. Gilbert AZ is NOT like Chattanooga TN, where there are flowers, pollen, leaves, bugs and more going into the pool!

Now, if you have a duststorm, things could change in a hurry!

[dubbedout]

Well, I am now a huge fan of adding a little DE into the sand filter! My pool is now sparkling clean just from adding the DE yesterday afternoon and running the filter for about 12 hours. And if all it takes is 1/3 cup this 25lbs should last me a lifetime! Thanks again Doc, now I now my filter is fine and I've also cleared up my pool!

[PoolDoc]

Great!

[CarlD]

Well, I am now a huge fan of adding a little DE into the sand filter! My pool is now sparkling clean just from adding the DE yesterday afternoon and running the filter for about 12 hours. And if all it takes is 1/3 cup this 25lbs should last me a lifetime! Thanks again Doc, now I now my filter is fine and I've also cleared up my pool!

Sounds about right! I haven't even finished going through the FIRST 10# box of DE I bought 4(?) years ago!