Retention Tank Vacuum Relief

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Asmart82

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What should I do to stop my retention tank from collapsing when I drain it or if there is no pressure from my pump but water is coming out due to gravity?

I have tried to find a vacuum breaker for PVC but everything I find looks strange to me so I am not sure what to get or how it works.
 

Reach4

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Take a look at Watts LFN36-M1

watts-lfn36-instructions.jpg
 
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Reach4

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Do not over-torque. Probably no wrench needed. I would use pipe dope or teflon tape.

When over-torquing into a schedule 40 female thread, you could split it.
 

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Valveman

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A pressure relief valve is not going to let air in the tank. Just put a tee in the line to the top of the tank. On that tee put a check valve with the arrow pointing towards the retention tank. The check valve in this direction will not let water out, but will let air in when under vacuum.
 

LLigetfa

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I'd use a footvalve rather than a checkvalve. They do the same thing but the footvalve has an inlet screen to keep stuff out.

Also, a some checkvalves rely on gravity to close. Make sure the valve is a spring loaded type.
 

Valveman

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I'd use a footvalve rather than a checkvalve. They do the same thing but the footvalve has an inlet screen to keep stuff out.

Also, a some checkvalves rely on gravity to close. Make sure the valve is a spring loaded type.

Good points. The screen on a footvalve is also not small enough to keep the bugs out. Probably should wrap a window screen over the foot valve or inlet to a check valve.
 

Reach4

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Is that a Clack RT120? Then one connection on top is labeled "Upflow Inlet", and that is connected to the dip tube. That I think is where the vacuum breaker is. The other port is the output, and is labeled "Downflow Inlet". I am trying to think if there would be an advantage to connecting the vacuum breaker to one port or the other, but I can't figure a significant advantage.



I still can't drain my retention tank without it collapsing.
Are you referring to opening the blow down port to drain sediment away? That would normally be done with the tank under pressure, with the pump kicking on as the pressure dropped.

If you were draining it empty with the pump off, the vacuum breaker should let the air in. I see the price of vacuum breakers increases quickly with size. Still, I would think that your 3/4 vacuum breaker should be able to admit air as quickly as you could drain water out. I don't know what causes your problem, unless your vacuum breaker is defective. Did you suck on it to see if it admitted air?

You need to protect those unpainted tanks, softener controller, and the PVC pipe from UV with a cover or paint.

clack-retention-tank.jpg
 
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MrTelco1948

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Saw a setup that had a drain valve after the tank output on top that was opened when filling tank and also opened when draining tank through the blowdown valve at bottom of tank. Tank was isolated with ball valves that served as a bypass when draining tank.
 
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