Two pumps with check valve in between ok?

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B

bhunjp

0
Aug 18, 2010
21
Central Florida
I am redoing my 20yr old hayward pump system with pentair intelliflo VS, intellichlor & a clean & clear 150.

I have two pumps ( pool & spa) with a spa spillover. I want to keep the current single speed spa pump.

This is a simplified version of my plumbing setup:

Code: 
Pool
Pump---Filter -->-|   
                  |             to spa return-->
                  |                    |
pool return --< 3waymanual --checkP>---T
                                       |
                                       |
                                       ^checkS
                                       |
                                     spa pump
                                       |
                                     spa drain

Any way - I am having my PB do the work. They came out and recommended getting rid of the spa pump and using the pool pump for the spa jets. The PB says it could cause excessive pressure if both pumps are on at the same time. They said if they keep the spa pump then they will not warrantee the plumbing against leaks.

I don't like losing the spa pump because then I lose control of the spa pump from the air switch next to the spa. Also, I don't want to have to invest in an automation system (intelli-touch...).

I think my system is ok because the check valve between the pool pump and spa pump (checkP in the diagram) will shut when the spa pump is running and all will be well. This should always be the case because the spa pump is fixed speed 3400rms and the intelliflo will be set to have a lower max rpm. Also, I have been using this system with both single speed pumps without problems related to the spa pump for 20 years.

So - the question is - Who's right?

Thanks,
B
 
Welcome to TFP!!!

Your logic makes sense to me and you have proven it to work for 20 years. I would not think that the pressure in the spa plumbing should be more than that generated by only the spa ... But ... there is an orientation that would clearly be bad ... but likely bad for the Intellifo.

If the 3-way valve ever was turned such that the pool return was closed and the spa pump was on, then the flow through the Intelliflo could stall and overheat.

As a note, it is generally better for the spa jets to not be running through a filter as that can add a lot of head loss and pressure on the system ... your configuration does not have that issue ... kind of a work-around from having to have a completely different set of plumbing for the jets and filtration.

Hopefully others will chime in, but I do not understand the PB's concern.
 
The way I see it, you are correct. Even if there wasn't a check valve you wouldn't overpressure the plumbing.

The way I understand it you can use the pool pump to run water through the spa but the spa pump won't run water through the pool. If that's correct then having two pumps will work fine.

The only possible downside I see is if the manual valve were turned toward the spa (closing off the return to the pool) and you ran both pumps, you could effectively deadhead the pool pump when it's running on low speed but since it's an Intelliflo VS it will sense no flow and shut itself down. If you were running the Intelliflo at full speed in that scenario you could effectively deadhead the spa pump but that's a very remote possibility.

Looks like the Intelliflo can produce about 95 feet of head (41 psig) and I don't know what the curve of the spa pump looks like so I don't know whether it or the intelliflo will produce the most pressure.
 
Thanks for the lightning fast replies!!

My install is two days away (Friday and it is Wednesday) so this information is invaluable. I agree that there is danger if the 3 way was turned the wrong way then the pool pump would dead head. However, I always set it so most of the water flows into the pool and the rest flows into the spa for the spillover. Hopefully I will only need one postion with the intelliflo.

By the way - does the intelliflo have protection against dead heading? Would it eventually detect this and shut off or does it only check for prime at startup time?

Thanks again,

B
 
If you were running the Intelliflo at full speed in that scenario you could effectively deadhead the spa pump but that's a very remote possibility.
Click to expand...

I agree that this is a remore possibility - The pool pump water goes through the filter and (I didn't mention this to keep the diagram simple) through solar panels. So the flow from the pool pump should be much less than the flow directly out of the spa pump at the check valve. Correct?
 
As Dave mentioned, the intellifo might sense a lack of flow and turn off (I am not sure).

Some 3-ways valves have physical stop tabs (I know the Pentair valves have external ones), that could be set to ensure the valve could not be turned to shut off the pool return.

Regarding solar, highest solar heating efficiency is acheived with the highest flow rates possible through the solar panels, often there is diminishing returns as you get above 1 GPM per 10 sqft of panels ... so a 50 sqft panel would want about 5 GPM. In my case I have 10 of them so good heating would be acheived with 50 GPM flow rate ... more flow rate could slightly increase the heating efficiencty, but would raise the pressure ... lower flow rate would have lower heating efficiency. So, first you have to ensure that your pump is running fast enough to prime the solar panels, then you have to decide your trade-off between running at high flow rate for best heating at higher electrical costs ... OR ... save $ by running at lower flow rates and getting less heating out of the panels.

To answer your question directly, the solar panels will add head loss, resulting in higher pressure and lower flow rates ... BUT, your pump is adjustable so that you can acheive whatever flow rate you want regardless of the headloss (within reason of course).
 
Don't install the VS or VF in this manner. The spa pump could force water past a check valve and cause anslow running variable speed to run backwards if enough water bypassed the check valve. This would cause the variable speed to run backwards and burn the windings. The pb is correct in not wanting to install it with a common run.
 
I just checked pentair's website and their check valve seals with a 1/2 psi. Assuming this is what my check valve could do couldn't we safely assume the spa pump would have more that a 1/2 psi over the pool pump. I'm not sure if my terminology is correct but it sure seems intuiitive that the check valve would seal with the spa pump running.
 
The check valves should offer the protection you need as long as they don't fail.

Also, the VS has several internal alarms that will help protect the pump.

1) Over heat & Over current alarms will protect the winding's from any kind of motor overload situation. So these alarms will trip well before the winding's are damaged.

2) Priming alarm. The pump can detect an under load situation which is alarmed as failure to prime. I don't know this for a fact but I my guess is that a pump under dead head will also trigger this alarm and shut the pump down.

But to me all of this is moot if the warranty is voided. That would be my main concern.
 

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I must have overlooked it - where does the spa drain end up? I assume back at the spa pump without going back through the pool loop - correct? Where does the pool flow that goes into the spa come back from also? I assume some overflow spill/waterfall - right?
 
Couldn't you rig a simple "automation" - when you switch the spa pump on - the 3 way valve is switched to pool only mode. It seems to me a single relay with a simple valve actuator might accomplish this. You might have to have another switch at the equipment to switch it back with another relay but probably not if you got creative. Essentially you would trigger the relay from the same switch that turns on the pump now.

Or am I overlooking something?

You'd still need the check valve because you'd turn the spa pump on during the activation of the valve and also "just in case" the valve didn't switch for some reason.
 
swimcmp said:
The spa pump could force water past a check valve and cause a slow running variable speed to run backwards if enough water bypassed the check valve. This would cause the variable speed to run backwards and burn the windings.
Click to expand...
I suppose it's possible for that to happen but I suspect the possibility is very small that it actually would.

I was reading the VS manual and it has blocked discharge and overheat protection, so it should shut itself down if the spa pump caused a severe enough issue to stop or reverse the flow through the main pump.
 
Here is a more detailed view of my plumbing:

Code: 
                                   Pool
pool Main Drain -->3way---3way-----Pump---Filter --solar-->-|   
pool skimm  -------^        ^                              |
                            |                              |
spa drain------------------|                                |
                                                            |            to spa return (jets) -->
                                                            |                   |
                                                            |                   |
                            pool return (pop ups) --< 3waymanual --checkP>-------T
                                                                                |
                                                                                |
                                                                                ^checkS
                                                                                |
                                                                                spa pump
                                                                                |
                                                                              spa drain

There is also a temperature controlled actuator solar bypass valve not shown.
There is also a 3way after the spa return (jets) that can put the water into the pool or the spa. I always have it set to spa only.
 
bhunjp said:
Here is a more detailed view of my plumbing:

Code: 
                                   Pool
pool Main Drain -->3way---3way-----Pump---Filter --solar-->-|   
pool skimm  -------^        ^                              |
                            |                              |
spa drain------------------|                                |
                                                            |            to spa return (jets) -->
                                                            |                   |
                                                            |                   |
                            pool return (pop ups) --< 3waymanual --checkP>-------T
                                                                                |
                                                                                |
                                                                                ^checkS
                                                                                |
                                                                                spa pump
                                                                                |
                                                                              spa drain

There is also a temperature controlled actuator solar bypass valve not shown.
There is also a 3way after the spa return (jets) that can put the water into the pool or the spa. I always have it set to spa only.
Click to expand...

Still a little lost about what happens when the pool pump is running and spa pump isn't; it appears in that case the spa drain goes to the pool filter - right? When spa pump is running but pool pump isn't - where does the water go - back to the spa pump bypassing pool filter?
 
UnderWaterVanya said:
Still a little lost about what happens when the pool pump is running and spa pump isn't; it appears in that case the spa drain goes to the pool filter - right? When spa pump is running but pool pump isn't - where does the water go - back to the spa pump bypassing pool filter?
Click to expand...

Sort of. The spa drain is only attached to the spa pump. When the pool pump is on and the spa is not, water is drawn from the pool only and returns to the pool and the spa (spilling over back to the pool).

When the spa pump is one, water is drawn from the spa and returns to the spa ... no filter in the loop, which is good for maintaining high flow to the jets.

I still do not really see a concern about the setup ... especially if it has worked for YEARS before with single speed pumps. Sure there are hypotheticals that might cause problems, but those conditions seem to have existed for a long time without issue.

EDIT: oh wait. Now I see that there is a spa drain 3-way on the pool pump. So I am confused now :) Is that connected to the same drains in the spa that the spa pump is connected to???
 
jblizzle said:
EDIT: oh wait. Now I see that there is a spa drain 3-way on the pool pump. So I am confused now :) Is that connected to the same drains in the spa that the spa pump is connected to???
Click to expand...

Yup - that's what tripped me up also.
 
Here is a more detailed description of the different mode:
Pool Pump Only:
The spa drain before the pool pump allows circulation of the bottom of the spa when only the pool pump is on. Pool pump only mode is about 99% of the time. This 3 way is set to a drain a small amount from the spa. It is just for a little circulation.

The 3 way between the pool return and the spa return is set just enough to the spa for a decent spillover when in pool pump only mode.

Pool & Spa Pump Mode:
When the pool and spa pumps are on the spa will eventually drain out because the pool pump will then return the spa water to the pool (check valve P closed). The spa pump returns all of the water to the spa. Ideally the spa drain 3 way before the pool pump would close when the spa is on. I don't have automation so this doesn't happen. It's not a big deal though. If we are in the spa long enough I will get out and change the valve manually. This rarely happens.

Spa Pump Only Mode:
When spa pump only mode the spa water will remain steady because all of the spa water is returned to the spa.

Make sense?
 
I talked to my PB today and he just does not like the check valve between the two pumps. I still don't understand the big concern. He says the pressure will be too great if both pumps are on and "the check valve will do nothing". I am going to test my current setup with the two single speed pumps to see what the filter pressure reading is with and without the spa pump on. If the pressure goes way up then I will have to agree with him. If it stays about the same then wouldn't that indicate the check valve kicked in and stopped the spa pump from pushing into the pool pump?

Anyway - I delayed the install until next Friday so that gives me some time. I may get another quote too.

Thanks all.

B
 

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