# Thread: How to figure flow rate

1. ## How to figure flow rate

I would like to put a timer on my pump. I have had my pool for 30 years and the pumps have never stopped pumping. I am on my 3rd Hayward 1 HP Super Pump. I would like to figure the turn over of my water so I can figure out how long to run my pump.

I have inground 18 x 36 pool approx 8 feet is 3 feet deep, then it slowly tapers to 9 1/2 feet in the deep end of the pool.
2. I draw water 1/2 from skimmer and 1/2 from main drain through 1 1/2 inch PVC plumbing.
3. Pump is wired 220 volt and only has one speed which is high.
4. S200 Hayward Sand Filter if that matters.

Can someone help me figure this out or tell me how to figure.

I do not have a flow meter installed.

Thanks

Tom

2. ## Re: How to figure flow rate

Flow rate depends on a lot of variables. Plumbing length and complexity are two key factors, and you may not even know how many elbows there are in the system. Pump run time will also affect your chlorination, skimmer effectiveness and your heater operation.

My thinking is that flow rate is a number used by the pool builder to choose the proper filter and pump for the pool. These components are usually chosen to give about an 8 hour turnover. I prefer the empirical approach to determining run time. Start with about 12 hours, and adjust it until you find a number that works. That time may vary during the year with pool usage, tree pollen, insect hatches or seeds. You may get better results if you split that time into two or more periods during the day. If there is no swimming, run time can be reduced to whatever keeps the pool clear.

3. ## Re: How to figure flow rate

as a quick guess looking over the hayward pump curves you are going to be getting around 100 gpm flow
im taking a guess on volume as im too mentally retarded right at the moment to figure out the metric equivilant but...

you should have around a 5 hour turn over, therefore run for 10 hours a day during summer

4. ## Re: How to figure flow rate

Originally Posted by JohnT
Flow rate depends on a lot of variables. Plumbing length and complexity are two key factors, and you may not even know how many elbows there are in the system. Pump run time will also affect your chlorination, skimmer effectiveness and your heater operation.

My thinking is that flow rate is a number used by the pool builder to choose the proper filter and pump for the pool. These components are usually chosen to give about an 8 hour turnover. I prefer the empirical approach to determining run time. Start with about 12 hours, and adjust it until you find a number that works. That time may vary during the year with pool usage, tree pollen, insect hatches or seeds. You may get better results if you split that time into two or more periods during the day. If there is no swimming, run time can be reduced to whatever keeps the pool clear.

and my thinking after running hydraulics training courses in NZ for the last 18 months after 10 years in this industry is that most builders have no idea why they put certain equipment or pumps onto pools, infact a common sales pitch is to offer to "upsize the pump"

i am of the firm belief that i would have virtually no pump problems or failures of builders new what they were doing, and in often let them know this.

You want to get 2 complete turns of water each day

5. ## Re: How to figure flow rate

Thanks to all.
Tom

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