Water Pump Suction mystery!!!

[Nodak7]

Ok this has been bugging me for awhile now. On our 2006 Hunter 41DS the water pump loses it's suction on the Port Tank. I have tracked this down and there are only 2 fittings between the tank and the pump suction. One fitting is at the tank outlet and the other is on the upstream of the suction valve. The tank fitting is tighter than hell and the valve fitting is a whale fitting. I believe that the only way that air can get into the line is at the whale fitting. It must be a very slight leak because it does not happen all the time but that is my only explanation. My question is is there a "check" valve on the suction line inside the tank which allows the water to drain from the suction line back into the tank? It doesn't seem plausible but??? I do not have any issues with the Starboard tank losing suction. Has this happened to anyone else? Any suggestions?

 

[Capt Robbie]

If your supply line from the tank is the plastic type like mine disconnect it from to the tank and from the pump. Drain all the water from the line, plug one end of the line and pressureize it with a shop vac or bicycle pump. You don't need a lot of pressure. Then take a sponge with soapy water and wipe down the entire supply line. You may have a slight crack in the supply line. I had a similar issues and found small crack in the line that drove me nuts for a year. It never leaked water but it allowed enough air into the system to create about 25% drop in pressure.

Hopefully this helps

 

[Nodak7]

If your supply line from the tank is the plastic type like mine disconnect it from to the tank and from the pump. Drain all the water from the line, plug one end of the line and pressureize it with a shop vac or bicycle pump. You don't need a lot of pressure. Then take a sponge with soapy water and wipe down the entire supply line. You may have a slight crack in the supply line. I had a similar issues and found small crack in the line that drove me nuts for a year. It never leaked water but it allowed enough air into the system to create about 25% drop in pressure.

Hopefully this helps

Now that sounds very plausible Capt! I just disconnected the hose from the valve and found no apparent issues. Cut a quarter of an inch off and reconnected it. I am trying it but it still seems to have some air when I turn on the spicket. You plan is next in line.... thanks

 

[seadaddler]

I had the 90 degree fitting at the tank constantly drip but no problem sucking air and pump worked fine and replaced the 90 degree fitting and no more drip.
Maybe the pump is sucking air and maybe the pump is the problem.
Nick

 

[Capt Robbie]

Good luck.
I found mine in a dip in the supply hose. I think water got trapped inside and froze and caused it to split. It was to difficult to cut out and splice a new section so I just used electical tape and wrapped it. So far so good it's been about fifteen years.
Hope yours is an easy fix.

 

[Tom J]

Don't forget the pickup tube inside the tank. We had the same issue on a commercial boat I worked on. Finally, we drained the water tank and found the pickup tube was rotted halfway down (steel tube).

 

[uncledom]

You might want to check for a blocked vent as a last resort also.

 

[jlp0217]

Like TomJ, I had a pinhole leak in the water pickup tube halfway down inside the tank. It was where the tube went through one of the baffles. Clue was that the first half tank of water worked fine, second half I had to let the pump regain prime before each use. When the water level got below that point, the pump would loose prime. I removed the tank & took it to a shop where they cut it open, repaired the tube, and welded it back up.

 

[Nodak7]

Like TomJ, I had a pinhole leak in the water pickup tube halfway down inside the tank. It was where the tube went through one of the baffles. Clue was that the first half tank of water worked fine, second half I had to let the pump regain prime before each use. When the water level got below that point, the pump would loose prime. I removed the tank & took it to a shop where they cut it open, repaired the tube, and welded it back up.

Thanks Tom! I am going to replace the suction line first and if that does not work then I guess I have to look at the pickup. But that will be a big job. The tank is buried under the sole plate.

 

[Don Lucas]

I'm going to admit that the last time I thought there was a suction problem from one of my water tanks I spend a bunch of time trouble shooting just to find at the end of it that ...................................................................................................... the tank was empty

 

[ice breaker]

Nodak. Access hole in floor is all you need to pull dip tube. Not a big deal.

If I were a guessing man, I would suggest checking all of the pex push connections. O rings fail, and given that you no longer need to winterize I would look at all of the fittings and o'rings......... that valve under the sink is a potential weak point....

All of the pex connectors on my boat are plastic. A cracked or stressed fitting would not surprise me. I had one break on the hot water heater, mid summer.

Good luck.