Upgrading to variable speed pump


New member
Apr 9, 2017
Monroe, LA
I just bought a house with an existing in ground pool. I calculated the pool to be 35500 gallons because it is L shaped with the following dimensions:
(40ft long x16ft wide x 6ft average depth x 7.5) + (15ft long x 15 ft wide x 4ft deep x 7.5). My existing pump was a WhisperFlo WFE-3 3/4HP which had a Centurion 1HP 3450RPM motor. The filter on the system is a Hayward S244T which is 24in and 3.14 ft effective filter area. The pipes on the system are 1.5in. There are no timers on the pump or power switch. There is a secondary pump for a Polaris vacuum which is on a separate pipe line. On that secondary line is an automated clorinator. I am unsure how to calculate feet head on the pool since I can't tell the way it was built under ground and there is not a working pump. I have two intake baskets and I am unsure about the number of drains due to the high level of algae. I live in Louisiana so I assume that the algae growth would be higher than average over the year.

When I initially opened the pool, I found that the Polaris pump was not working. I ran the pool filter pump for a few days with success. All the debris was cleared from the pool and pulled into the skimmer basket. There was still algae on the bottom which needed to be vacuumed, so I called a man to clean it. After backwashing the sand filter and whatever, he reported that my pool pump had broken. I brought the current configuration and dimensions to a local dealer and they sold me a 2.5 HP Jacuzzi Variable Speed pump.

Based on my pool size I think the existing sand filter is too small and that possibly the original 1 HP pump was too small. However, I think that 2.5 HP may be too big for my current filter and 1.5 inch pipes. I will have to downsize the connections to install the pump and the manufacturer only recommends 2 inch pipes. I wanted to have the energy efficiency of the variable speed pump, but I don't want to waste energy on more HP. The other concern is the GPM rating on the filter is 62. Will this pump damage the filter? Should I replace the small filter with a larger one due to the size of the pool? Will I negate the energy savings with this pump on a 1.5 inch pipe based on these curves?


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

Welcome to TFP.... A Great resource for all your new pool and pump questions... :lovetfp:

The great thing about a variable speed pump is that you do not have to worry about its HP rating, because you basically only use what you want.

Kind of like your car.. Has a ton of HP but you seldom use all of it.

I have a couple of rent houses with 3 HP VS pumps and they both have 1.5" plumbing. The pumps have been running for several years without any issues.

As far as energy savings goes, I can run my 3 HP Intelliflo, at 1,200 RPM, 24/7 for less than $20 a month. VS pumps are very efficient and very quiet at low speeds.

Thanks for posting and good luck with your new pump,

Jim R.