Will water flow from elevated SPA back down to POOL if there is a High-Loop and Pool Supply check valve in our automated system?

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T

TaylorN

0
Sep 7, 2018
111
San Diego
Pool Size
23500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
Quick question that has been bugging me for years.

When the automated valves (via daily schedule) are in between transitioning from POOL and SPA mode (they take about 20-30 seconds to completely transition), will the water flow from the SPA through the pump, over a high loop (higher than the top water level of the SPA), and back into the pool if there is a check valve on the POOL supply pipe? Note, there is no overflow/waterfall from SPA to POOL. They are treated like different bodies of water, and the Jandy Iqualink controller switches between POOL and SPA once a day to generated chlorine and filter the water in each body of water.

Currently we have no check valve on the POOL supply pipe, and everyday 0.5" water drains from the SPA into the POOL do to gravity while the automated valves transition from POOL to SPA and then later back to POOL again.

Of course, if I install a check valve on the POOL supply pipe I would have a definitive answer, but the piping is complicated and I would have to also replace 2-3port valves which I don't want to do unless also installing a check valve on the POOL supply pipe guarantees to solve the "problem" (ie SPA water level drops 0.5" per day).

My guess would be that with a check valve on the POOL supply line gravity would not allow water to naturally flow up and over the high-loop because there is nothing kick starting that flowing process? Unless the water, post high-loop, has enough suction (falling back into the pool) that it continues to draw water up and over the high-loop from the SPA until the valve transition completes.

See attached diagram with proposed new Check valve in black. Note, the check valves would/are of course be above ground (the brown line), but to keep the diagram simple, they are shown below ground.

Any thoughts?

Thanks!
 

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You can't put a check valve on the inlet side of a pump that restricts water from flowing into it. Can water flow over that loop (commonly called a Hartford loop)? Yes, if it is airtight as a siphon effect can occur. If there is an overflow setup in your system, a .5" drop is nothing over which to be concerned as it will be refilled the next time the pump runs. As long as the water level is at the tile there is no issue.
 
TaylorN said:
Note, there is no overflow/waterfall from SPA to POOL. They are treated like different bodies of water, and the Jandy Iqualink controller switches between POOL and SPA once a day to generated chlorine and filter the water in each body of water.
Click to expand...
1poolman1 said:
If there is an overflow setup in your system, a .5" drop is nothing over which to be concerned as it will be refilled the next time the pump runs. As long as the water level is at the tile there is no issue.
Click to expand...

There is no overflow in the OPs system and so the spa will not refill without adding fill water to it.

In my view this is a design flaw in your system. If you have 2 bodies of water sharing equipment you need a spillover. Otherwise you need 2 sets of equipment. Or an autofill should have been installed in the spa.

Is the pump running when the system changes modes? Try changing modes with the pump stopped.
 
Thanks for the quick replies.

I have modified the configuration so when the transition takes place the pump is on, and have also set it so the pump is off during the transition. They yield about the same level of water drop.

As for an auto fill, that would indirectly just keep adding more water to the Pool, since it would be the final location of the top offs.

As for a check-valve on the inlet side of the pump, if it is located far enough away (say 2 or 3 feet) i dont see why that would be too restrictive. Those jandy check valve flaps crack open (allowing water to flow) really easily, and comversely would prevent the flow backwards into the pool. I could even use one of the larger 2.5/3in check valves to be extra conservatice. i of course would replumb the current inlet to the pump , which would mean moving the supply valve (spa/pool selection) further away, and would place the check valve just before the supply valve but after the main drain and skimmer valve (which currently there isnt enough room to put a check valve in there).

But if water does actually flow through the high loop, then there is no point in replumbing everything to incorporate a check valve.
 
TaylorN said:
I have modified the configuration so when the transition takes place the pump is on, and have also set it so the pump is off during the transition. They yield about the same level of water drop.
Click to expand...

That indicates the water is siphoning with gravity to the pool.

You need to confirm if the siphoning is through the returns or suctions. Using some winterization plugs you can plug the return or suction pipes and cycle the vales and see if water is lost.
 
Yeah, you are right, I could block off the cleaner's ("The Poolcleaner") suction pipe and the skimmer suction pipe and then manually flip the valve actuators at the same time. if I lost water, then the water did go through the high loop and out the pool return lines. If there is no water loss, then it didn't make it through the high loop and adding the check valve would probably do the trick then.....?

I was just hoping someone was a master hydraulics physicist and I didn't have to experiment :ROFLMAO: but that experiment seems easy enough. Thanks!
 
Trust but verify. I would not do anything without physically verifying it first.
 
TaylorN said:
I was just hoping someone was a master hydraulics physicist and I didn't have to experiment :ROFLMAO: but that experiment seems easy enough. Thanks!
Click to expand...

Since you requested a master hydraulics physicist let's invite @mas985 to comment.
 

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TaylorN said:
When the automated valves (via daily schedule) are in between transitioning from POOL and SPA mode (they take about 20-30 seconds to completely transition), will the water flow from the SPA through the pump, over a high loop (higher than the top water level of the SPA), and back into the pool if there is a check valve on the POOL supply pipe?
Click to expand...
Yes, most definitely water will siphon out of the spa suction through the filter past the check valve, over the high loop and out the pool returns. There is nothing to stop it.

But water also goes from spa suction out through pool suction AND spa return out pool return.


TaylorN said:
Currently we have no check valve on the POOL supply pipe, and everyday 0.5" water drains from the SPA into the POOL do to gravity while the automated valves transition from POOL to SPA and then later back to POOL again.
Click to expand...
That wouldn't help because water can still travel as outlined above.

TaylorN said:
Of course, if I install a check valve on the POOL supply pipe I would have a definitive answer, but the piping is complicated and I would have to also replace 2-3port valves which I don't want to do unless also installing a check valve on the POOL supply pipe guarantees to solve the "problem" (ie SPA water level drops 0.5" per day).
Click to expand...
Don't bother, won't solve the problem. Again, flow goes from spa suction to pool return with nothing to stop it.

TaylorN said:
My guess would be that with a check valve on the POOL supply line gravity would not allow water to naturally flow up and over the high-loop because there is nothing kick starting that flowing process? Unless the water, post high-loop, has enough suction (falling back into the pool) that it continues to draw water up and over the high-loop from the SPA until the valve transition completes.
Click to expand...
Static head due to elevation changes offset each other. This is called a siphon. Having that loop is completely worthless as it is now.

TaylorN said:
See attached diagram with proposed new Check valve in black. Note, the check valves would/are of course be above ground (the brown line), but to keep the diagram simple, they are shown below ground.
Click to expand...
Won't do diddly

TaylorN said:
Yeah, you are right, I could block off the cleaner's ("The Poolcleaner") suction pipe and the skimmer suction pipe and then manually flip the valve actuators at the same time. if I lost water, then the water did go through the high loop and out the pool return lines. If there is no water loss, then it didn't make it through the high loop and adding the check valve would probably do the trick then.....?
Click to expand...
The high loop will only stop flow IF it is filled with air instead of water.

So, if you want to break that siphon, install a vacuum release valve on the top of the hump so when the pump shuts off first, that pipe will drain of water (one side only because of the existing check valve) breaking the siphon. However, this does not actually solve the problem because the spa suction will still drain through pool suction and spa return drain through pool return. So you would need a check valve on the pool suction and spa return.


With that type of setup, there really should be two sets of equipment.
 
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mas985 said:
With that type of setup, there really should be two sets of equipment.
Click to expand...
Absolutely. Builder didn't do any favors. Problem:
RS6+2 chip - $650.00 (if board is new enough to accept the chip)
New, separate, filter - +/- $700.00 (200sq. ft.)
New pump (that will communicate with the Jandy) - $1500.00 (if it is just for filtration).
Possibly separate heater if pool is also heated - $3100.00 (400K if the water is not kept heated)
These are approximate retail, online costs, plus labor to install and possible electrical and gas line upgrade.
Space on the equipment pad is now at a premium.
Half inch of water - now priceless and cheap.
I've put these bids together in the past and no one has ever thought it worth the cost, even the guy who was spending near $1,000,000 to remodel his already expensive house. I knew the contractor. Made me almost wish I was still a construction contractor.
 
mas985 said:
The high loop will only stop flow IF it is filled with air instead of water.

So, if you want to break that siphon, install a vacuum release valve on the top of the hump so when the pump shuts off first, that pipe will drain of water (one side only because of the existing check valve) breaking the siphon. However, this does not actually solve the problem because the spa suction will still drain through pool suction and spa return drain through pool return. So you would need a check valve on the pool suction and spa return.
Click to expand...
Thanks! That's exactly the definitive answer I was looking for.

There is already a check valve on the spa return, so its really then just the addition of a check valve on pool suction and add vacuum release valve on top of high loop. Probably not worth the 0.5" per day, but going to keep the solution in my back pocket for now. Again, thank you!
 
1poolman1 said:
Absolutely. Builder didn't do any favors. Problem:
RS6+2 chip - $650.00 (if board is new enough to accept the chip)
New, separate, filter - +/- $700.00 (200sq. ft.)
New pump (that will communicate with the Jandy) - $1500.00 (if it is just for filtration).
Possibly separate heater if pool is also heated - $3100.00 (400K if the water is not kept heated)
These are approximate retail, online costs, plus labor to install and possible electrical and gas line upgrade.
Space on the equipment pad is now at a premium.
Half inch of water - now priceless and cheap.
I've put these bids together in the past and no one has ever thought it worth the cost, even the guy who was spending near $1,000,000 to remodel his already expensive house. I knew the contractor. Made me almost wish I was still a construction contractor.
Click to expand...
Yeah, that would be crazy
 
TaylorN said:
Thanks! That's exactly the definitive answer I was looking for.

There is already a check valve on the spa return, so its really then just the addition of a check valve on pool suction and add vacuum release valve on top of high loop. Probably not worth the 0.5" per day, but going to keep the solution in my back pocket for now. Again, thank you!
Click to expand...
Remember that a check valve in the suction line that will prevent water from flowing that direction will stop the pump from getting water when it is on. Water would have to be able to flow in the direction of the pump in the suction line, and that is the likely way it is traveling now with the pump off and the valve turning.
You could try one of these, with the full 5# springs installed (it comes with multiple springs for various needs), but that would mean the pump would have to work very hard to prime and keep water moving if it could. Never tried it.
  1. Flo Control 5 lb. Clear Compact Spring Check Valve 2" | 1795C20
 
TaylorN said:
Thanks! That's exactly the definitive answer I was looking for.

There is already a check valve on the spa return, so its really then just the addition of a check valve on pool suction and add vacuum release valve on top of high loop. Probably not worth the 0.5" per day, but going to keep the solution in my back pocket for now. Again, thank you!
Click to expand...
The only other option would be if there was a product or controller configuration so the return valve actuator would start first and finish before the supply/suction valve actuator starts changing. pool supply/suction check valve in place, the spa supply/suction side would not have anywhere for the water to go. Too bad there can't be a programmatic staggered start of the actuators.
 
1poolman1 said:
Remember that a check valve in the suction line that will prevent water from flowing that direction will stop the pump from getting water when it is on. Water would have to be able to flow in the direction of the pump in the suction line, and that is the likely way it is traveling now with the pump off and the valve turning.
You could try one of these, with the full 5# springs installed (it comes with multiple springs for various needs), but that would mean the pump would have to work very hard to prime and keep water moving if it could. Never tried it.
  1. Flo Control 5 lb. Clear Compact Spring Check Valve 2" | 1795C20
Click to expand...
Yeah, I actually had bought a 2lb spring check valve with a similar thought (definitely not 5lb!), but didn't have the stomach to install it on the SPA supply/suction side. Would have also benefited from mounting higher in the air so it wouldnt have to hold back as much water/gravity. 2lb spring would probably work if the mounting height was perfectly balanced so it only took a little suction to open the 2lb spring
 

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