Air in fresh water system when tank is half full.

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bobeast

Dance the Tide
SILVER Sponsor
Oct 22, 2017
2,829
Isleton, CA
Boat Info
2002 310DA
Engines
350 MPI w/V-drives
Hi All. I'm putting this in general since I assume my issue is not model specific. When my fresh water tank is about half full, I start noticing sputtering when I turn on a faucet. My theory is that there is a crack in the pickup tube inside the tank which gets exposed when the tank level drops. At that point, the pump starts sucking in air along with the water.

In researching tank fittings, I was unable to find a fitting that had a "dip-tube" and I am more than likely not using the correct terminology.

Any thoughts on what kind of fitting I should be searching for, or even if I am on the right track?
 
You could try "withdrawal tube" or "withdrawal assembly". That definitely is a term in the fuel tank world.
 
Tman said:
You could try "withdrawal tube" or "withdrawal assembly". That definitely is a term in the fuel tank world.
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Thanks. I did look at those, but they all seem to be ¼" for fuel tanks. I'm thinking I need ½". I'm amazed that this is so difficult to find, as I would expect it to be a common part. I may end up having to glue in a length of PEX, but I'm not quite ready to go hillbilly yet.
 
Garden hose would be questionable but your potential to use PEX makes it first class hillbilly.
 
I've usually seen them called "pickup tubes"... maybe that would help? Not sure if there is a space between the K & U, though. PVC pipe would likely stay straighter over time than Pex. I kinda think that's all it is to begin with - PVC or CPVC.
 
Lazy Daze said:
I've usually seen them called "pickup tubes"... maybe that would help? Not sure if there is a space between the K & U, though. PVC pipe would likely stay straighter over time than Pex. I kinda think that's all it is to begin with - PVC or CPVC.
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Thanks Dennis. I searched for that as well, and just came up with through-hull fittings to pull water from the outside. I may just use a Uniseal flange with a length of ½" PVC. I can then just home depot the rest of it.
 
Does your existing pick-up tube just unscrew from the tank? How much clearance do you have above it... enough to maybe bend the pick-up tube out? Note that I'm now using a hyphen... in your parts catalog (part #1127935) it's labelled that way.

But I don't see anything wrong with your idea. Should work just fine - after all, it's just a tube.
 
I just went through this earlier this year, finding the correct supply (dip) tube was tough. My original was a section of 1/2 clear lexan fitted to a nylon hose barb fitting, i tried to repair, didnt work. I built a new one, mine was 1/2 in.mpt x 5/8 hose barb ell tank fitting. I opened up the I.D. of the threaded end with a 1/2 in bit, epoxied a piece of 1/2 pvc tube into the fitting, cut pvc proper length, done.
 
Lazy Daze said:
Does your existing pick-up tube just unscrew from the tank? How much clearance do you have above it... enough to maybe bend the pick-up tube out? Note that I'm now using a hyphen... in your parts catalog (part #1127935) it's labelled that way.

But I don't see anything wrong with your idea. Should work just fine - after all, it's just a tube.
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It probably did unscrew before the %^#^%# boat yard used 5200 to "seal" it. As it is, I'm going to have to cut a new hole and plug the old one.
 
Jandcinok said:
I just went through this earlier this year, finding the correct supply (dip) tube was tough. My original was a section of 1/2 clear lexan fitted to a nylon hose barb fitting, i tried to repair, didnt work. I built a new one, mine was 1/2 in.mpt x 5/8 hose barb ell tank fitting. I opened up the I.D. of the threaded end with a 1/2 in bit, epoxied a piece of 1/2 pvc tube into the fitting, cut pvc proper length, done.
Click to expand...

Thanks! I'll try the Uniseal route and keep your solution in my back pocket, for if that doesn't work out. My guess is, that all these tanks have a "pieced together" solution and that no one manufactures a complete assembly. That would explain why googling reasonable descriptions didn't yield any results.
 
Just for kicks, try looking at Todd Marine Products. But, yeah, all it is a fitting and a pipe and is easy enough to replicate.
 
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