Pump turnover rate

[waldreps]

How can I calculate how long it takes for my pump to turnover the water in my pool? I don't see a GPM rating on my pump only horsepower. Is there some calculation I can do or am I missing something? Thanks.

Stacy

[duraleigh]

Hi, Stacy,

You should be able to find the "pump curve" for your model on the manufacturers web site. use 50-60 head for an IG pool. That'll get your prettyclose on gpm for your pool.

[waldreps]

Ok, here's the deal....I have an AO Smith motor using a Hayward Super Pump strainer and impeller. Should I just assume that the AO Smith motor is an exact replacement for the original Hayward motor and look at the Hayward info? The motor was replaced before I bought the house.

[mas985]

This is the third thread on this topic and probably deserves a sticky but anyway here is what I posted on the other threads:

Turnover is the time it takes for the volume of the pool to run through the pump. However, this does not mean that all of the water has gone through the pump. Some water goes through once, some twice and some not at all. It depends on the plumbing, returns, skimmers and drains. To determine turnover:

First, determine the head loss for your plumbing. A rough estimate is to take your PSI from the filter and multiply this by 2.31. If you do not have a vacuum gauge, add about 10' of head for suction head. Otherwise, multiple the vacuum (in. mg.) by 1.13 to get suction head. Add return head and suction head to get total head.

Second, look up the the flow rate from the pump head curve. Usually in the pump manual.

Third, use the formula turnover (hrs) = Pool Volume (gallons) / (gpm * 60)

Also, you should be able to find the pump curve on the Hayward site.

[waldreps]

Thanks for the info, that's what I needed. According to those figures and my numbers, looks like my pump needs to run close to 24/7 to turnover the water twice each day as I have heard is recommended. Thanks.

[Phillbo]

Twice a day turnover does not sound right ..

[mas985]

Yea, a 12 hour turnover would seem to be on the high side. Either you have a very large pool or a 2 speed pump operating at the lowest possible speed. Many pools have pumps with very high HP and short turnovers 2-4 hours. What head calc did you come up with and what HP pump do you have?

[waldreps]

I have an AO Smith 1.0HP pump with an SF of 1.40. I don't know how to calculate all the suction and return head stuff, so I just used the rough estimate of multiplying 2.31 x 17psi (from the gauge on my filter after backwashing) = 39.27. According to the pump chart that would be 65gpm but my filter is only rated at 52 so I used 52gpm. My pool is about 30,000 gallons and that comes out to be 9.6 hours for one turnover. So, two would be 19.2 hours which is pretty close to 24/7. Did I do something wrong? I was trying to determine if I should install a timer and not run the pump 24/7, but for 5 hours I'm not going to worry with it.

[mas985]

You also need to add the vacuum head which for your case may be around 10 ft. So your total head is about 50' which is normal for a pool. Also, even though the filter is rated at 52 gpm, it does not mean it limits the flow only that damage may occur after 52 gpm, so your flow can still be higher.

[Poolsean]

Its common for pool contractors to size the equipment accordingly. The pump is sized to provide enough circulation to filter the whole pool once every 8 hours. Then once this is determined, the filter is sized to accomodate the flow rate.
DE filters can handle twice the flow rate that the filter is rated for (65 sq ft filter can handle 130 gpm). Cartridge filters are equivalent (100 sq ft filter can handle 100 gpm). Sand Filters are usually rated for 15 gpm per sq ft of filter area (7 sq ft sand filter can handle 95 gpm).

The horsepower x service factor is your true motor horsepower output.
Your 1 hp pump x 1.4 sf = 1.4 HP (use the pump curve for 1.5 hp)

Hope this helps.