1994 300' DA water pressure (tank) issue

frosh coach

frosh coach

Member
Apr 20, 2011
237
Long Island Sound, New Haven CT
Boat Info
1997 300 DA,
1994 300 DA (SOLD)
1989 230 (SOLD)
Engines
Twin Mercruiser 350 FWC, 300 HP MPI V-drives
I Replaced my water heater and all plumbing after the pump with PEX last week.

The pump was running and would not build enough pressure before the replacement, and the same thing is still happening. When hooked up to the dockside it works great. I'm thinking there is either air source between the tank and the pump. I'm also assuming there is a check valve that stops the water when hooked to the dock from filling the tank. Maybe the valve is gummed up... It's driving me nuts.

anyone else experience this before?
 
Often the pump is the "check valve". Follow your plumbing - specifically where the dock water plumbs into the system and also the output side of the pump to be sure.

First things first... is the tank full? Disconnect and reconnect the line at the tank and where it connects to the pump. Also, go back over everything you've installed to make sure it's pushed in all the way. You can find out if there's an issue with the tank fitting/dip tube by eliminating the tank from the equation... instead of the pump drawing from your tank, temporarily plumb it to draw from a 5g pail.
 
Lazy Daze said:
Often the pump is the "check valve". Follow your plumbing - specifically where the dock water plumbs into the system and also the output side of the pump to be sure.

First things first... is the tank full? Disconnect and reconnect the line at the tank and where it connects to the pump. Also, go back over everything you've installed to make sure it's pushed in all the way. You can find out if there's an issue with the tank fitting/dip tube by eliminating the tank from the equation... instead of the pump drawing from your tank, temporarily plumb it to draw from a 5g pail.
Click to expand...

Lazy Daze - i'm going to try the 5 gal bucket. I found some water (~1.5 gal) next to the tank. I'm starting to wonder if the tank might have a leak some where.

The tank is full. If i find out it's pumping from the 5 gal bucket, i'll drain and pull the tank to have it pressure tested.

I don't think the new pex is leaking as it works great off the dock water and i haven't observed any leaks.

i'll post back after I try this.
 
Have you changed out your pump yet?

I bet the diaphragm is shot.

Depending on the pump you can change out the entire head for about $70.
 
While a leak in the tank is still an issue, it wouldn't cause the problem you are having. As long as the dip tube and associate plumbing to the tank are good (and the bottom of the dip tube is in water), a leak won't affect drawing water out.

Disconnect/reconnect the line at the tank and where the line connects to the pump before you do anything else - you might get lucky... then you can deal with the leak. I'm just going to go out on a limb here, though, and fathom a guess that the leak is from either the tank fitting or the line to the pump. That would, at least, possibly explain both issues you are having.
 
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