Flow between pool and surge tank

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Abdulellah said:
also to ensure that the pump does not exhaust its capacity in suction side , since the non-return valve is exposed to high hydrostatic pressure due to the pool.
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In my opinion, this is not an issue at all.

You have a flooded suction because the pump is below the surge tank.

As long as the pipe is sized correctly, the head loss and NPSH are going to be good.

The back pressure on the check valve is only the height differential from the surge tank water surface to the pool water surface, which is 1.4 meters (4.6 feet or 2 psi) when the pump is off.

This will keep a vertical ball check valve or a vertical swing check valve closed.

Once the pump is on, the check valve opens and the water will flow without a problem.
 
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A swing check valve requires some back pressure to seal.

You will have about 2 psi.

The swing check valve without a spring requires about 3 psi to close.

2 psi will probably work if the flapper opens upward.

Some swing check valves have a spring that will assist the valve in closing.

The Praher models have some that will probably work.

Check with your supplier for a swing check valve in 5" or 6" with a spring assist close and mount it opening upward if possible.
 
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Hart loop with a vac release valve. I’ve installed a few for infinity edge pools that have had issues with draining. Just a T and bushing in the hart loop and vac release valve. 3CDABF16-B5AA-4088-9113-F6CB8E797BBC.jpeg
Note the hartloop would be on the return side of the pump.
 
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The vac release won't help if the main drain is tied into the suction line.

If the main drain goes to the surge tank and you only have a suction line from the surge tank, it could work, but I would still put 1 or 2 check valves on the system after the pump.

You also have to figure out how to route the loop above the pool which can be awkward.

In my opinion, a 5" or 6" swing check valve with a spring assist close would be a better choice.

The 4" spring check valve can be used instead of the swing check valve if you want a more secure close.

Also, having a check valve on the suction has a higher risk of getting debris stuck in the valve unless you have a strainer before the check valve.
 
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The D110 4" spring check valve has about 3 psi of head loss at 264 gpm.

66 cubic meters per hour is 290.6 gallons per minute.

The 4" spring check valve might work as long as you have a strainer before the check valve and you limit the flow to about 250 gpm.
 
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I agree I would still use check valves. The vac release would be a fail safe. I would have a designated pump for the surge tank and a designated filtration pump for main drain.
If plumbing doesn’t allow a 2 pump system, I would eliminate the drain suction. Just pull from the tank filter and return. Like a gravity skimmer.
 
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Why wouldn’t you be able to have the suction side solely attached to balance tank and filter and return to the pool with check valves and vac release? Adequately sizing the balance tank is another headache. I’ve seen spas with similar setups. I think a two pump system would be the most ideal. Unless I’m completely missing the point of the balance tank.
 
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You can have the main drain go to the balance tank, but by having a separate main drain suction, you can shut down the balance tank if you need to work on it and you would still be able to circulate the pool using the main drain.

It also allows you to adjust the amount of water going over the edge into the gutters because you can control the flow from the main drains and the gutters separately.

You can put all of the flow on the gutters or the main drains or any combination that you want.

If the main drain line goes to the balance tank, you can control the amount of flow from the main drains but not the flow from the gutters unless you close the line to the balance tank.

That also requires a float valve and the balance tank might need to be bigger.

The point of a balance tank for a gutter overflow or infinity edge is because you can't put suction directly on either one.

The water from the balance tank and from the main drains should be filtered.

It doesn't make sense to send the water back to the pool without filtering.

Many infinitely edge pools have an infinity edge pump with no filter, so some people don't use a filter for an infinity edge but I think that a gutter overflow will usually have a filter.

You can put a separate pump and filter on each line if you want.

It seems like an unnecessary expense.
 
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In my opinion, using 2 spring assisted swing check valves and a strainer before the check valves would be the best choice.

I would have a valve before the strainer and unions on the check valves so that they can be serviced.

I would have 2 spare check valves that are easy to swap out as needed.

I would keep the flow below 6 feet per second in every suction line.

I would use 5" PVC for each line.
 
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Pentair has some commercial strainers that would be helpful if the gutter water is going to contain anything that could clog or interfere with the check valves.

The bronze would be a better choice than cast iron because cast iron will rust and cause iron stains.

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www.pentair.com

Hair and Lint Strainers - TradeGrade

Forged from cast iron or red brass for heavy-duty service, in a variety of pool and spa applications.
www.pentair.com www.pentair.com
 
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