Should I replace my 1 1/2 HP pump?

JayH

Active member
Jun 3, 2018
35
Bucks County, Pa
Hello!
I have a Doughboy 18' x 33' swimming pool with a deep end holding about 17,000 gallons, I guess, and I have a 20" sand filter with...you guessed it a 1 1/2 HP single stage motor. I also have replaced the flexible tubing with pvc and have installed a second return port on the opposite end of the pool for better circulation.
This filter is costing me $174 per month assuming 2.14 KWH x 24 hours x 30 days.
Is a two speed a good choice? If so what brand is a good one?
Or is a variable speed a better choice?
Thank you.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,950
Bedford, TX
Jay,

I can't help with the specific pump but I can give you an example of the savings..

I have a 3 HP VS pump that I run 24/7, most of the time at 1200 RPM.. My cost is so low that it does not even show up on our electrical bill.. I calculate that the cost is less than $20 bucks a month.

With your pool I would vote for a 2-speed pump.. It will save almost as much as a VS pump and would work better for you. You would run on low speed except when vacuuming or if you wanted to a quick skimming..

Thanks,

Jim R.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,669
Pleasanton, CA
The cheapest short term solution is to run the pump only a couple hours a day. You should not need anywhere near that amount of run time. How are you chlorinating the pool?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
13,950
Bedford, TX
PM,

About 165 or 175 Watts... It ranges between those two valves, but seems to change a little whenever I look at it..

Thanks,

Jim R.
 

JayH

Active member
Jun 3, 2018
35
Bucks County, Pa
Thank you both for your replies.
For chlorination I am using liquid chlorine. My cyanuric acid level and hard water pretty much prevent me from using any tablets that I have found but if I could I would, I just seem to get better results with them.
 

Oly

Gold Supporter
Jun 28, 2017
1,123
Fresno, CA
Ask yourself if you need the 1.5hp.
Do you use a pump driven pool floor cleaner?
How many skimmers in your pool?
Any water features or solar heating systems that use the pump?

I replaced a 2hp single speed pump with a 1.5hp VS and never run it at full power (2400rpm max) and my answers to the above are; no, 1 and no.
 
  • Like
Reactions: markayash

JayH

Active member
Jun 3, 2018
35
Bucks County, Pa
Oly, good questions. I do have an inexpensive fountain that the kids like ($35). I don't have a pump driven floor cleaner. I have one skimmer. I don't have, or plan to get, any heating system. All good points.
I don't understand the no, 1 and no part of your answer though. Thanks.
 

Oly

Gold Supporter
Jun 28, 2017
1,123
Fresno, CA
What are your answers to my 3 questions?
edit: Answered before I responded.
 
Last edited:

JayH

Active member
Jun 3, 2018
35
Bucks County, Pa
I did find these two pumps. A Hayward SP15932TL with 1 1/2 hp, 12 amp and 3 amp. A Pentair 347992 with 1 1/2 hp, 16.4 and 4.4 amps. Running 3 amps would run me $29 per month.
 

Oly

Gold Supporter
Jun 28, 2017
1,123
Fresno, CA
I don't understand the no, 1 and no part of your answer though. Thanks.
Those were my answers to my questions.
I found a lower hp pump to be sufficient for my simple system.

Regarding a 2-speed pump on low, it probably will not push the water fountain the same. The question is will it be sufficient flow on the low speed for the skimmer to clean the surface. If not then you are stuck running it on high. While it is more expensive a variable speed pump will provide you the options to adjust and fine tune the flow rate for maximum efficiency (effectiveness and lowest cost of operation).
 
Last edited:
  • Like
Reactions: JayH

JayH

Active member
Jun 3, 2018
35
Bucks County, Pa
This is more challenging than I expected. According to Hayward..."Circulating 7,000 gallons with a PowerFlo Matrix model # SP15932S would take about 113 minutes at high speed and about 9-3/4 hours at low speed, depending on the filter paired with it. The pump motor is rates at 1.265 kW/h at high speed and 0.334 kW/h at low speed."
At the low setting there isn't enough hours in the day to circulate the amount of water that the EPA recommends, 4 times in 1 day.
If my math is correct I have about 17,000 gallons, times 4 = 68,000 divide by 24 = 2833 divide by 60 = 47 gallons per minute.
Now, to find out how to pair a pump with my sand filter that does this on low I guess (or variable speed).
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,669
Pleasanton, CA
We don't subscribe to the turnover theory on the forum. 2-4 hours of run time is sufficient for circulation. Please read the pump run time study in my sig.

If you have only one skimmer, a two speed on low should be sufficient for it to work properly. Most skimmers only require 10-15 GPM for debris capture.
 
  • Like
Reactions: JayH

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,669
Pleasanton, CA
I would get a two speed AG pump. Dynamo, OptFlo, PowerFlo Matrix are all good pumps. The smallest you can find should be sufficient.


One of the more economical VS pumps might be more suited for an AG pool. Something like this:


BTW, what was your old pump model?

A third option is to replace the motor on your current pump with a two speed motor although it will probably cost almost as much as a new pump. But it will be easier to install as no plumbing changes are required.
 
Last edited:
  • Like
Reactions: Oly

JayH

Active member
Jun 3, 2018
35
Bucks County, Pa
mas985, thank you for telling me about some models that can be a good option for me. It sounds like either one is an improvement.
The pump I have now is probably better known by another brand to those who know but I only know it as a Doughboy XP-1.
Although I would economically prefer the lower cost of the two speed I may (keyword: may) end up getting the variable speed to, as Oly pointed out, "provide you the options to adjust and fine tune the flow rate for maximum efficiency".
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,669
Pleasanton, CA
You are going to pay a bit more for a 115v VS pump;


The added efficiency of a VS pump sometimes doesn't pay for the extra cost of the pump. A two speed captures most of the savings at close to half the cost. If you run the economics on both pumps, the VS would probably not pay for the extra cost over the life of the pump.
 
  • Like
Reactions: JayH

cj133

Well-known member
May 6, 2018
206
NJ
I'm using a Hayward Matrix 2 speed 1.5HP pump with a 250LB sand filter and run it 24\7 on low speed.
My pool is only a 15 x 24 and holds approximately 8500 gallons so I really don't need to run the pump 24\7 but for the cost, I see no reason not to.

I use high speed if people are in the pool or if I'm vacuuming.

To be honest, for me the skimmer tends to work better with low speed because the water isn't as agitated even with the return pointing slightly downward. Of course, other setups will probably behave completely different.

That said, after using a 2 speed pump I can't see ever going back to a single speed ever again. So either 2 speed, or variable.
 
  • Like
Reactions: JayH