Please help guesstimate my GPM

mr ken

Member
Apr 29, 2008
21
I am looking to get a new pump as my 14 year old motor may be deteriorating...
I posted on another thread that I was looking to get a whisperflo full rated 3/4 hp or 1/2 hp. or a dual speed....
I have only 1 1/2 inch pipes , so gpm are an issue,,,,mas 985 has been very helpful in education me.

I have now just found the paperwork of my current 14 year old pump...

It is a Jacuzzi magnum plus with a magnatec Centurion switchless motor...
It is 1 hp and an SF of 1.2 and is 60hz...

With this unit and 1 1/2 inch pipes, there are 1 suction line 50 feet from skimmer basket,,,,1 suction dedicated line for an automatic cleaner that I have never used or even opened, 2 return lines of 20-25 feet with eyeball jet caps...
no waterfalls or spa or extras..

How many GPM am I putting out with my current magnatec Centurion system..it was installed 1995, so I got good use from it..
Thanks
Ken
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,800
Pleasanton, CA
Because the SF of your current pump is only 1.2, this pump would actually have less flow rate than a full rated 3/4 HP Whisperflo which has a braking HP of 1.25. So my guess would be about 50 GPM with your current pump. The 3/4 HP Whisperflo will probably get you closer to 58 GPM.
 

mr ken

Member
Apr 29, 2008
21
mas985,
Thanks
so would I still be ok with the full rated 3/4 hp whisperflow or go with the full rated 1/2 hp whisperflo.
If I went with the dual speed , I would have to go with the 1hp which has the 230 v...The 3/4 dual speed has only 115v set up and I currently have 230v with my current system...
According to Pentair the 1 hp dual speed on hi speed will push 90 GPM at 50 ft of head, so with my 1 1/2 inch pipe this may not be prudent...

Which single spped whisperflo full rated should I go with the 3/4 hp or the 1/2 hp...
Thanks
Ken
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,800
Pleasanton, CA
If you can change the electrical to 115v which is not hard to do, your best option is to go with the 3/4 HP 2 speed. You can simply use one line of the 220v with the addition of a neutral line which should be in the electrical box. High speed would be close to what you have now and low speed would save you 35% in energy costs.

Otherwise, the next best option would be the 1 HP but I would only run that on low speed.