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Gibsonguy

Piercing a hole in copper discharge pipe of sump?

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Hello Everyone,

I inspected an early 1960's home, original on owner. The discharge pipe for the sump pump is copper and the water was squirting out the side of the pipe. I thought it was the weld, but the owner told me the pump company had told him to put a hole in the discharge pipe to help relieve pressure because the discharge pipe runs 8 ft high. Anyone heard of this? The pipe does have a one way valve on it.

I have never seen this before.

Once again, thanks in advance for all your wisdom.

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Hi Marc

It is below the check valve, right after the pump. The discharge tube runs from the pit up to the ceiling, and then horizontal, where the check valve is installed. His explanation was to relieve the pressure in the pipe. My question is.. because of the strength of the pump? To empty the pipe because it is 7 ft or 8 ft high? I've never heard of it being done before, yet he states the company asked him for it.

When the pump operates, obviously it sprays out from the hole, but the pump operates sufficiently to empty the pit.

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That's pretty common. As you guessed, the idea is to allow the pipe to drain so that the poor pump doesn't have to fight the head pressure on start up.

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Found this from Frank the Plumber, a guy in Chicago.....

"The principles of fluid dynamics are such that a liquid may act as a solid in a static position.

In this static position the fluid may be more prone to act as a solid if there should be added pressure.

Said pressure is exerted by the fluid column that is trapped between the pump outlet and weir of the drainage outlet.

In a case where the pump base sits in a 36" deep pit and exits to a pipe at 7 feet above floor the water column may be 10 feet. If you took that 10 feet and filled a bucket with it you may have 3 gallons of waterX 8 = 24 ponds of fluid pressure applied, calculate the check flap resistance into the equation and you may fluid lock a pump.

Thus by relieving the water column at the base of the pump you allow the pump to discharge unloaded and allow the velocity of this water discharge to lift the check and properly function.

Over the course of a pumps life this elimination of load may earn the pump a 5% capacity towards life and 5% power savings as most pumps elevate their power usage per the respected load applied."

Seemed like a decent description.

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High head pressure can complicate a piston pump trying to start. As mentioned by others, a pressure relief is common but this 'hole' method is new to me.

Marc

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It's in the instructions of every pump I have installed.

Flotec: Drill a 3/16" (5 mm) hole in discharge pipe about 1 to 2"

(25-50 mm) above pump discharge connection (but below

check valve) to prevent airlocking the pump.

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I looked up 'airlocking' because the term doesn't make sense. I understand it now and it's a misnomer but let me run it past the brethren so I'll know if I got it right:

When there's no air at the high point, the fluid just downstream of the high point generates a suction in the same way that pulling a filled straw out of a glass of water does so. This suction force aids the pump as it tries to push up fluid on the upstream side of the high point.

If air occupies that high point as well as a sufficient portion of the piping downstream of the high point, the suction is lost. More pressure from the pump is needed to move the fluid through the circuit. If it can't generate that extra force, the fluid doesn't circulate.

Is this correct?

Marc

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Airlocking is not locking anything, you are right.

Old timers remember pouring water into the hand pump to prime it.

What Jim said, releasing the water reduces the head at startup, a cheap centrifugal pump way down in a pit.

A good quality submersible well pump has no problem pushing a head of 150 feet and more.

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