pool pump size for 12.5k gal pool

[PoolDoc]

Not sure who you are asking, but the big current problem with the Pentair products is the drastically curtailed warranty on DIY, non-contractor installations.

[slythic]

The question was directed towards you PoolDoc! Since this ppgmeasap asked a similar question to one I asked on this thread a few days ago :-)

I was basing a lot of my initial choices based on your sticky post titled "Recommended equipment for new inground pool" which recommends Pentair pumps and filters. Do you recommend switching my choices to Hayward due to this DIY warranty issue? I particularly like that the Pentair manual for cartridge itself recommends the use of DE (best of both worlds).

[TomC]

Ben , correct me here if I'm wrong, or just delete my post. I had a discussion with a Pentair rep about adding some DE to the cartridge filter. He said that cartridge filters filter better when a little bit dirty. So they recommend on start up to add a little DE to jump start this process. Since my current cartridges are a couple of years old, I no longer do this because I never really get them that clean. If you do add DE just add a little through your skimmer line, maybe a half a cup.

On another note, I must say that my 2 speed Whisperflo pump is great. When on low speed, which is almost all the time after initial cleanup, it is 1/4 horsepower. Enough for a good flow through the 6 returns but not enough to get water up to the slide, for that I run it on high, which turns it into a 1 1/2 horsepower pump. This is plenty for my pool. It's a simple pump with no fancy electronics to burn out.

Tom

[PoolDoc]

Ben , correct me here if I'm wrong, or just delete my post. I had a discussion with a Pentair rep about adding some DE to the cartridge filter. He said that cartridge filters filter better when a little bit dirty. So they recommend on start up to add a little DE to jump start this process. Since my current cartridges are a couple of years old, I no longer do this because I never really get them that clean. If you do add DE just add a little through your skimmer line, maybe a half a cup.

Do NOT do that! (Add DE to a cartridge filter.)

Unicel is the leading US cartridge filter maker, and makes a number of the OEM cartridges used by the major US pool equipment companies. Their national sales manager is a member here (though not too active) and I've talked to him several times. He told me that the DE particles both embed in the cartridge fibers and can't be removed, and actually cut or otherwise damage the fibers.

DE in DE filters? OK, obviously. DE in sand filters? Helpful for special purposes, such as trapping particles otherwise too fine to catch.

DE in cartridge filters? Turns out, that's a really bad idea.

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Regarding pumps: what you describe with respect to your Whisperflo is pretty much what would be expected. But the Whisperflo is a high flow / high power pump, and is too MUCH flow for a 12.5k gallon pool. One issue is backwashing sand filters: too much flow will wash sand out on each backwash.

One of the benefits of the VS pumps is that they can be 'turned down' to match pool size, but still remain efficient. To match a 2 speed Whisperflo -- efficiently -- to a 12.5k gallon pool you'd need to buy the 1HP 2 speed, and then take it apart and replace the 1 HP impeller with the 3/4 HP impeller. (They don't make a 2 speed 3/4 HP pump, so you'd have to do it yourself.)