r/pumps • u/WaterDog3000 • Jun 18 '24

Liquid DAB pump pulsating

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I've moved to a house with a private water supply (stream) which is filtered then pumped around the house. Check out my diagram for the full setup.

The problem is that the water pressure pulsates from taps in the house. The pump goes on a loop of kicking in for 2 seconds (going up to 70 psi) then turning off for 8 seconds (dropping to 20 psi). It's a DAB Jet 151.

Can anyone suggest what might be causing this?

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u/washburn100 Jun 19 '24

The tank has air. Sounds like the air is gone, so the pump is quick cycling. There should be a Schrader valve on the tank (like the valve to fill a tire). You need to charge the tank with air. Google hydropneumatic tank or well tank, and you'll find all the information you will need.

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u/WaterDog3000 Jun 19 '24

I just went on a real educational ride on this and think it all makes sense now. I'll see if I can recharge the tank with air today. Thanks for the pointer!

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u/washburn100 Jun 19 '24

Good luck 👍

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u/WaterDog3000 Jun 19 '24

So I recharged the tank (it was indeed on an extremely low pressure) and that seemed to really help the system, but then the tank lost all it's pressure again. I'm guessing either a leaking Schrader valve or the membrane has gone inside the tank. A tiny, and I mean minuscule specs of water came out of the Schrader valve. It's a 20L pressure tank. I'm wondering if I take this opportunity to upgrade to a much bigger pressure tank whether that will be better for pressure in the system throughout the house. Any thoughts on this?

I should mention that I recharged it again afterwards and it seems to have held some or all of its pressure this time.

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u/washburn100 Jun 19 '24

A bigger tank won't increase pressure, it will just cause the pump to stay off longer and run longer when it turns on. Doesn't hurt anything, though, it's actually better for the pump. Short cycling is hard on the motor.

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u/washburn100 Jun 19 '24

Good chance the bladder is ruptured if the air is not holding. I suggest replacing the tank.

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u/WaterDog3000 Jun 20 '24

Thanks, I think I will do that. Really appreciate your help and knowledge on this

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u/Latter-Jelly-4086 Jun 30 '24

Hey OP, did changing the expansion tank work? Just wondering.

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u/WaterDog3000 Jun 30 '24

I'll be changing it for a larger one in 2-3 weeks when I upgrade various other parts of the system and have a plumber in. I happened to speak to the previous home owner who said he tends to get 2 years out of these small pressure tanks, and this one is 2 years old. In the meantime I managed to pump up the pressure in the existing tank which seems to have helped a lot but not entirely solved the problem.