Swimming Pool Pump And Filter Too Big?

by Steve Doty
(Caseyville ILL.)

I have a pool that's 18'x42" and a swimming pool pump filter system that's for a 24'x 48" pool.

My question is can I use this big of a pump on this much smaller pool and what if any problems will I have.

Thank you

Thanks for your question Steve

Without knowing the horsepower pump, diameter of your swimming pool plumbing, and pool filter size, I cannot tell if it's the right size or not. Some 24' X 48' pools may have a 1 or 1.5HP motor which will probably be too big for the pool you have now. I can give you some general rules and guidelines to follow.

After this you can look for yourself or get a qualified pool tech. This is what I know.

The pool filtration system is based upon the volume of water in the pool, the diameter of your pool plumbing and the size of your filter.

First you need to know the volume of the pool. This should be easy for you.

Then the swimming pool plumbing capacity needs to be addressed. For example, a 1.5" pipe can handle no more than 44 Gallons Per Minute (GPM), and a 2-inch pipe, 73 GPM.

Most pools have a minimum of 2 intake lines: the skimmer(s) and the main drain. On a pool with two 1.5" suction lines, the maximum flow rate capacity is 88 GPM because you can double the GPM, but only if it also has at least two return lines of the same size. The returns or outflow is just as important as the inflow or suction when you're choosing a pool pump.

Filter flow rate is the third factor. Swimming pool filters to do their job according to the type and size of the filter which is measured in square feet.

You can find the optimum and maximum flow rates of the filters in the owner's manual and on the information plate attached to the filter.

Here's the catch:

There are those that might want to sell you on a horsepower motor rather than what's best for your pool. They sell "free upgrades" or 2 HP pool pump motors when you might just need a 1.5 HP or even a .5 HP pump motor.

It might be too much if you have a 1 1/2 or 2 horsepower pump motor. What happens is that the water is going through the plumbing too quickly.

Also, with that much water going through the lines, it creates somewhat of a "whirlpool" effect in the pool water. You want the water coming out of the returns to flow into the water nicely and gently, otherwise the dirt and debris will just be kicked around.

The only way to know your GPM is to install a GPM meter.

The calculations are are follows:

Pool Volume (gallons) X 2 = gallons required daily for a 12 hour turn-over


*A pool that holds 15,000 gallons of water
*15,000 gallons X 2 turnovers per day = 30,000 gallons/day

* You need to circulate 30,000 gallons of water every 24 hours

Now the GPM

*30,000 gallons ÷ 24 hours = 1250 gallons per hour
* 1250 gallons per hour ÷ 60 minutes = 20.8 gallons/minute (GPM)

If you need to downgrade to a smaller pool pump size, say 1/2HP, you can look into 2-speed and variable speed pump motors. These will save you money in the long run because they're not going a full throttle all the time.

It's my belief that many swimming pool pump motors are WAY TOO big for the pools. Pool owners get into the "bigger is better" mindset and that's not always the right choice. Nice and easy is the way to go and filter.

I know this is not a yes or no answer, but you need to have all the information you can when making the right decision for the best pump motor for your swimming pool.

I hope this helps and answers your questions

All the best


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Pool & Filter Plumbing

by Bruce

I have 8000 gallon inground pool with 1 hp heyward super pump. is it possible to use high pressure tubing from pump to filter? Thank you.

Hi Bruce. If you're asking the question, can I replace the usual PVC pipe with flexible high pressure tubing and it be as effective as PVC pipe, my answer would be you would need to contact the Hayward to get that specific question answered. I've installed dozens of filtration systems and have always used PVC pipe for the GPM required and for the Feet of Head Calculations.

As a pool professional I cannot give you the go-ahead to make such a modification. Not only are you talking about possible warranty issues but safety issues as well. There is a school of thought about rigid PVC compared to flexible PVC. Kuriyama of America is a large distributor of flexible PVC. My understanding is they actually discourage pool owners to use flexible PVC in inground pools. You can contact them for more information.

Hope that helps.


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