2nd pump might be pulling sand into pool

Jrindin

Member
May 28, 2018
20
Germantown/TN
We had a pool built last summer. The builder did a lot of weird things one of which is using two pumps with one before the sand filter and the other after. The pool has a spa and the intention was that when the valve is set for the spa, the 2nd pump can be turned on to increase the flow rate. That does happen but I also notice after I've run both pumps that there is sand in the spa. I also notice that the pressure is zero on the pressure guage at the filter.

Has anyone ever seen this configuration? Is it possible that pulling water from the filter instead of pushing water to the filter can cause the sand to get pulled out of the filter?

This config has always seemed like a bad idea anyway. I'm thinking about re-plumbing so that the two pumps are in parallel feeding the filter with backflow valves on each pump for when only one is running.

Thoughts?
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
113193

The flex hose on the left is now permanent plumbed waste line. main pump is the one in the middle. fed by spa drain, pool drain, skimmers. two valves after the chlorinator are for spa jets and pool jets. after spa valve is electric heater and 2nd pump. The valves are horrible. I want to redo the whole thing but do it right this time.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
12,960
Northern NJ
The place where your pool builder cheaped out is not putting in a separate floor suction in the spa dedicated to the second jet pump. That is typically what is done. Then the second jet pump has its own closed loop of water source from the spa and return through the spa jets.

Post pics of the data plates for the two pumps. I wonder if one 3HP VS pump can sufficiently power your spa jets at max RPM. Vary the RPM and flow of one pump rather then having two pumps. Your signature says you have a 1.5 HP and a 1 HP pump. Can an Intelliflo 3HP VS pump do the same work?

Putting in Pentair automation with Jandy valves and actuators and a VS pump is what I woudl consider.

@mas985 @JamesW may have thoughts on alternative pump setups.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,931
Pleasanton, CA
The PB put the pumps in series which increases the flow rate a little bit but not as much as if they were plumbed in parallel. But the sand in the spa is a little troubling. The combination of the two pumps could very well exceed the recommend flow rate of the filter. It would have been more advisable to put in a filter bypass instead to run the spa jets.

What size is the filter?

What are the two pump models?

How many spa jets do you have and what are their sizes?
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
The place where your pool builder cheaped out is not putting in a separate floor suction in the spa dedicated to the second jet pump. That is typically what is done. Then the second jet pump has its own closed loop of water source from the spa and return through the spa jets.

Post pics of the data plates for the two pumps. I wonder if one 3HP VS pump can sufficiently power your spa jets at max RPM. Vary the RPM and flow of one pump rather then having two pumps. Your signature says you have a 1.5 HP and a 1 HP pump. Can an Intelliflo 3HP VS pump do the same work?

Putting in Pentair automation with Jandy valves and actuators and a VS pump is what I woudl consider.

@mas985 @JamesW may have thoughts on alternative pump setups.
That would have been nice... The floor of the spa would be all drains since you'd need two more I'm guessing though. I'd like to be able to run both of these pumps for the pool itself as well to get better water movement at times. I'm in Memphis and we have 75 ft pines that like to do a mass drop once a year. Pine needles float so putting the skimmers on turbo would be helpful.

I definitely agree that the VS pump would be the answer but if I can get away with using what I have since I just bought them last year, that would be best since my investment will be the time to rework the pad. I'll will certainly look into automation with jandy valves though.
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
The PB put the pumps in series which increases the flow rate a little bit but not as much as if they were plumbed in parallel. But the sand in the spa is a little troubling. The combination of the two pumps could very well exceed the recommend flow rate of the filter. It would have been more advisable to put in a filter bypass instead to run the spa jets.

What size is the filter?

What are the two pump models?

How many spa jets do you have and what are their sizes?
Here's what I think the filter is:
Model NumberFilter DiameterFilter Area
(ft2)
Pipe SizeDesgn Flow Rate (gpm)Maximun Working Pressure
(PSI)
Media Requires*
(lbs)
Carton
Dimension (inch)
BC305422"2.691 1/2"455025023 x 23 x 38


Pumps are Reliant CS4M249I1L (1hp) and CS4M257I1L (1.5hp)
There are 6 jets that are the same size as what is in the pool. The opening looks like maybe 1/2".

Yes, I found a paper on pumps in parallel vs in series and it looks like they come close to delivering full flow for each when both are running. I'm thinking there should be check valves on the pipe leaving each pump so that they there's no re-circulation back through the non-operating pump when only one is in operation.
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
Here's what I think the filter is:
Model NumberFilter DiameterFilter Area
(ft2)
Pipe SizeDesgn Flow Rate (gpm)Maximun Working Pressure
(PSI)
Media Requires*
(lbs)
Carton
Dimension (inch)
BC305422"2.691 1/2"455025023 x 23 x 38


Pumps are Reliant CS4M249I1L (1hp) and CS4M257I1L (1.5hp)
There are 6 jets that are the same size as what is in the pool. The opening looks like maybe 1/2".

Yes, I found a paper on pumps in parallel vs in series and it looks like they come close to delivering full flow for each when both are running. I'm thinking there should be check valves on the pipe leaving each pump so that they there's no re-circulation back through the non-operating pump when only one is in operation.
And pipe size is 1 1/2". Starting to get a bad feeling about my filter size and pushing 2.5hp gpm through 1 1/2" pipe...
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
I'm thinking you guys are going to tell me my filter is undersized. So, if I were to put set the filter valve to recirculate when I crank up the 2nd pump, is that the same as adding another valve to bypass the filter using pipe?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,931
Pleasanton, CA
I'm thinking you guys are going to tell me my filter is undersized. So, if I were to put set the filter valve to recirculate when I crank up the 2nd pump, is that the same as adding another valve to bypass the filter using pipe?
Yes the filter is undersized (as well the pipe) and yes you can use bypass while in spa mode as a temporary solution.

Also, running the main pump with the second pump off is very inefficient because the first pump is pushing water through the impeller of the second pump that is off. It is high restrictive and significantly reduces the flow rate of the main pump.

But longer term, you might consider a re-plumb.
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
For now I'm going to re-do the pad with the pumps in parallel and bypass the filter when I use the 2nd pump. Just put the pool in last year and can't imagine what ripping out all the pipe would cost.

Thanks for your help on this. Disappointing that my PB was so inept. I just replaced two of my lights and replaced the transformer because he undersized the transformer and the lights burned up. I had to do it myself because he wouldn't respond. Not really much recourse there other than posting negative remarks, which I haven't done YET.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,931
Pleasanton, CA
You might find that the flow rate of the larger pump by itself is not that much less than the two in series. In other words, you may only need one pump with a plumbing partial bypass. I am currently running 6 spa jets with a 1 hp pump (separate loop) but the pipe is 2.5" which helps quite a bit. Do you know the orifice size of the jet nozzles?
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
nozzle size is 3/4", I believe. They are the same as the pool jet nozzles. I'm going to put the pumps in parallel and hope for the best. To your point, they're doing no good at all in series with the 2nd not running and I have to bypass the filter when the 2nd IS running. If it turns out I can't run the 2nd pump then I'll at least have a hot swap pump in case the main pump goes bad.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,931
Pleasanton, CA
Those are the wall fittings (aka eyeballs). The jet nozzles are deep within the spa wall and are usually 3/8" but can be 1/4" or 7/16". This determines how much flow rate you need.

But when you put them in parallel, you will need a check valve to prevent re-circulation at the return port in the pump that is off.
 

Jrindin

Member
May 28, 2018
20
Germantown/TN
I'm fairly certain there are no jet nozzles in my spa. Are those to facilitate a blower which I don't have? Our spa is more like a creek with some current than a turbulent spa. :(

Yes, I did think about the check valve(s). I'm going to put one at the exit of both pumps so that I can use either by itself.

If I knew then what I know now...
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,931
Pleasanton, CA
Ok so I guess they did not use venturi tees? There may not not be a blower but there would be an airline for the bubbles if you did have venturi's.