Is .5HP Enough?

[Steve E]

So my pump stopped working and I'm looking at buying a new one. We don't want to spend the big bucks for the super fancy ones at this time. I went into the local pool shop and they are suggesting a .5hp pump. My current pump is 1.5hp and the pool is roughly 20,000 gallons. I'm concerned that .5 hp won't be enough and will have to work harder to keep the pool circulated. Am I off on this or is the guy at the pool shop correct in saying .5 will be fine? There are no water features or anything.

Thanks!

 

[jblizzle]

HP of the motor does not tell the entire story. You need to tell us the Service Factor (SF) of the motor as well as the type of pump you have and are considering.

There are certainly some pumps that can use a lower HP*SF motor and move more water than a different pump with a higher HP*SF.

 

[sktn77a]

Look at the labelled HP and SF of your existing pump. Does the pump work well? compare this with the HP and SF of the pump they are suggesting. I understand going down some as most pool pumps are oversized. But a drop from 1.5 to 0.5 is quite a bit and I wouldn't do this without a lot of analysis and discussion.

 

[Steve E]

This is the pump I'm looking at: Hayward Tristar .5hp https://www.hayward-pool.ca/shop/en/canada/tristar-inphtris--1 HP is .5 SF is 1.98

The pump I'm replacing is a Hayward Superpump 2, 1.5hp https://www.poolsuppliescanada.ca/hayward-1.5-hp-super-pump-inground.html HP is 1.5 SF is 1

Thank you

 

[jblizzle]

So the Tristar is a 1 HP*SF and the Super Pump is a 1.5 HP*SF.
But, the Tristar is a larger pump than the Super Pump.
You can pull up the performance curves and compare the flow rate at a common Head loss to compare performance.
My guess is that the Tristar will move more water than your previous pump and may even use more power.

- - - Updated - - -

Why not just replace the motor on your existing pump? Maybe with a 2-speed version?
Then there would be no plumbing changes required.

 

[DDGMAN]

This is a great reference: https://www.youtube.com/watch?v=cqBaDmKrPGI

 

[jblizzle]

I am 20% of the way into that video and already disagree. There is no need to worry about flow rates or turn overs.
All is well and good until you they ask you to calculate the average feet of head ... that is not trivial.

Having skipped through the rest of the video ... there is no need to do anything in that video.

The pump should be as small as will give adequate circulation, coupled with as large a filter as you can justify.