Determing ideal pump size

[tangouniform]

My original Hayward Sta-rite 1-speed 1.5hp pump has bit the dust. One problem that I've always had with this pump was what might be considered cavitation. When using my suction-side vacuum from my dedicated suction port, I would have to have at least one skimmer valve open to bring in enough water to not run the pump dry, however this affected the cleaning effect of the vacuum. So I think this might have been caused by my pump being too powerful. None the less, I'm looking for a new pump now. I'm looking at the Pentair SuperFlo 1HP 2-speed, but I want to make sure this will be enough umph considering the distance from my pad to pool. Specs below:

Pipe size: 1.5"
Filter: 24" sand (Triton II TR-60)
Suction lines: 4 (2 skimmers, 1 main drain, 1 vacuum)
Returns: 4
Distance from pad to closest skimmer: 35'
Distance from pad to main drain: 50'
Distance from pad to furthest skimmer: 65'

So given the above, would ya'll agree that the 1.5hp might have been overkill and that a 1hp would be more than enough? It's the way I'm leaning now, but I'd hate to under-power my setup.

 

[Bama Rambler]

IF you were getting air into the pump strainer basket when vacuuming it wasn't because the pump was too big. It was because you had/have a suction leak somewhere that only shows up under suction pressure. Changing pump sizes may not fix that problem unless the leak was on the suction of the pump itself.

Having said that. going to a 2-speed 1hp pump is a good idea and that pump should be a good fit for your pool.

 

[BoDarville]

A couple of things to consider in sizing a pump:

1. You need to know the design flow rate of the jets to determine the ideal pump size.
2. Maximum GPM rating for filter size.
3. Do you have a pool/spa heater (Assuming no based on your pool specs)
4. I don't see any water features listed (e.g., spa, fountains, waterfall), so I'm assuming none.

Based on the above assumptions, your pool specs, and the equipment specs of some of our Expert members, a slightly smaller pump than your current one should work fine. Also, keep in mind that selecting a 2-speed pump would give you the best of both worlds. When sizing pumps, be aware of the Service Factor HP (SFHP). This is determined by taking the rated HP and multiplying it by the Service Factor. For example, 1 HP pump with a Service Factor of 1.1 would have a SFHP of 1.1.

More detailed information about pumps & sizing is found here: Hydraulics 101 - Have you lost your head? Post # 2 contains more info about sizing pumps.