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Old 07-08-2008, 11:07   #1
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Bleeding Fresh Water System

Just recently changed out my fresh water pump. Loud knocking occurs when the faucet is turned. Is there a recommended procedure for bleeding the system? (I am assuming the noise is from trapped air)
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Old 07-08-2008, 11:44   #2
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If you have an accumulator tank, there may be a pressure or bleed screw on it. The knocking sounds like "water hammer". In systems without an accumulator, there may be a vertical pipe stub (a dead end vertical pipe, capped at the top) that is designed to prevent water hammer, too. Normally that's got no provision for bleeding, but if it leaked or was removed, could cause the same problem. If the new pump is stronger than the old one, and there was no accumulator tank before? Adding an accumulator tank would solve the problem, and make the pump work less, too.
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Old 07-08-2008, 11:54   #3
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Air in the system will result in spurts out of the faucet and if the tank or lines are emptied you need to run the pump with all faucets open including hot water until water flows without air. The hot water tank needs to be full of water and not partially filled with air. The knocking may be your pump not fastened down. If you have rigid water lines then some may be hitting the hull as the water pulses until the air is gone.
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Old 08-08-2008, 21:38   #4
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Start with the faucet furthest away from the pump.

What type of freshwater pump are you using?

Some have a hard time priming.

Remove hose from outlet side of pump and turn on till you get water.

Are the tanks full?.... (seriously...this happens frequently)
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Old 09-08-2008, 02:13   #5
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You are all right, this knocking is "air hammer".

I installed a bleeder valve on Southbound. This was just a “tee” fitting with a valve on the open end, inserted in line just after the pressure water pump. To bleed the water lines, you open the bleeder valve, and let the pump run until you get “airless” water.

Without a bleed valve, open up your plumbing pipe/hose at the lowest practicable point, or the nearest faucet.

Then open faucets one at a time, starting at next nearest, and run till airless.
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Old 09-08-2008, 05:24   #6
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Without a bleed valve, open up your plumbing pipe/hose at the lowest practicable point, or the nearest faucet.
I find I need to open more than one faucet. I open all 4 galley and the head faucets since they are closest to the pump. The pump can't push air against water that well so it does relieve the resistance in front of the pump until the pump has water to it. I only have to do this if the tank sucks air. The T fitting after the pump would work much better. I use one before the pump for winterizing.
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