2 pump design for pool and spa

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J

Jrindin

0
May 28, 2018
20
Germantown/TN
I had a new pool and spa build this summer. The contractor plumbed it where the spa/main/skimmer returns feed pump 1 (1.5hp), then to the filter, then to the pool jets and spa jets.

The spa and pool jets have valves as do the returns. after the spa jet valve there is the heater and pump 2 (1hp).

The problem is that I can only use pump 2 for the spa and when it runs it pulls water away from the pool jets and I have to open the spa jet valve to utilize pump 2. I would like to move pump 2 so that is is fed by pump 1 before the filter so that when I want 2.5hp of pump I can turn them both on and I can divert full power to either the pool or the spa or balance the flow between the two.

Has anyone done this? Seems like a 1hp and a 1.5hp pump in series both on would behave like a 2.5hp pump and if I wanted to turn off the 1hp pump that it would just be passive.

Make sense or should I draw a couple pictures?
 
Not the best practice to plumb two different pumps together. However it can be done.

It wont result in 2.5 hp. It will result in something else. At a guess 1.9 hp or similar. Effectively the smaller pump will have to overcome the 'pressure' of the larger pump to get its water out and this is where the loss of power is.

Personally I would way prefer the two pumps in front of the filter. There are a million reasons why, and it is best practice for microbial destruction. However it is also unique to my world view to date.

Before we go ahead and plumb like this we need to do some numbers to see if it can be made to work. To do the numbers, I would need pump make and model (both pumps), filter make and model, gas heater make and model and a photo of the equipment pad so I can see if it can work. I should also point out the normal outcome is I end up with an extra filter in the circuit as the single filter cant usually handle the required flow.
 
Some pics of your current equipment pad would let us see what you are starting with.
 
You can see the 1hp pump is after the heater. They are actually in series now but the 1.5hp pushes to the filter and the 1hp pulls. I think ideally I replace the 1.5 hp with a variable 2.5hp and take out the 1hp altogether but that will obviously cost more and we just had the pool built and the budget is well beyond what we intended to spend already.

If I can make this work and just re-plumb that would be fantastic.

Thanks for taking time to help me figure out how to optimize what was done here.
 
Jrindin said:
I had a new pool and spa build this summer. The contractor plumbed it where the spa/main/skimmer returns feed pump 1 (1.5hp), then to the filter, then to the pool jets and spa jets.

The spa and pool jets have valves as do the returns. after the spa jet valve there is the heater and pump 2 (1hp).

The problem is that I can only use pump 2 for the spa and when it runs it pulls water away from the pool jets and I have to open the spa jet valve to utilize pump 2. I would like to move pump 2 so that is is fed by pump 1 before the filter so that when I want 2.5hp of pump I can turn them both on and I can divert full power to either the pool or the spa or balance the flow between the two.

Has anyone done this? Seems like a 1hp and a 1.5hp pump in series both on would behave like a 2.5hp pump and if I wanted to turn off the 1hp pump that it would just be passive.

Make sense or should I draw a couple pictures?
Click to expand...

With pump 2 off.

Take a pressure reading on the gauge at the filter with pump 1 running.

Adjust the valve I have circled in pink so the pressure gauge moves up a smidgen in my language we would look for 10 kPa increase. This gives a positive flow to pump 2.IMG_0870.jpg

Now start pump 2.

Has this fixed the issue you are reporting?
 
We might have crossed wires a bit on this. What I'm trying to figure out is if I move pump 2 to be inline with pump 1 before the filter, will I get the equivalent of 1.5hp using pump 1 and 2.5hp when I turn on pump 2 for when I want more water flow to the spa. You can see they're inline now but pump 2 is after the spa valve and I don't like it there.
 
Jrindin said:
We might have crossed wires a bit on this. What I'm trying to figure out is if I move pump 2 to be inline with pump 1 before the filter, will I get the equivalent of 1.5hp using pump 1 and 2.5hp when I turn on pump 2 for when I want more water flow to the spa. You can see they're inline now but pump 2 is after the spa valve and I don't like it there.
Click to expand...

Sorry. I read the initial issue as pump 2 was pulling the water away from the pool jets. Adjusting the valve will likely solve this issue.

I am actually a fan of putting the pump before the filter for other reasons. However it means upsizing the filter as the flow combined will be above the breakthrough point - breakthrough is a term we use for the water and dirt pushing all the way through the filter and out to the pool again. Most domestic filters calculate to breakthrough before a reasonable run time between backwashes. Putting two pumps on it will make this worse.

Is this a cost willing to be accepted? I can then calculate and sketch a general layout. Two additional check valves will be required.
 

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