R27 2012 Fresh Water Vent

[royf]

We received the boat late last season and found the fresh water tank didn't seem to be venting properly. The symptoms included:
1) When filling the tank, no air noise or overflow water seen at the vent.
2) After screwing in the filler cover, water pressure would reduce until hardly any water would come from the faucet. On opening the filler cap there is a big hissing sound as the vacuum in the tank is equalized. Then the water pressure would be fine again for a bit.

Yesterday, I decided to see if I could confirm the vent line is not kinked or compressed in some way. I removed the refrigerator and disconnected the vent tube from the hull opening. Nothing obvious was wrong. I put some air pressure in the tube, but it seemed to be either clogged or has a check valve (unlikely).

I couldn't see the tank connection from the fridge compartment, so I wasn't able to confirm anything on that end of the vent tube.

I spent about an hour searching through the forums and couldn't find an previous post that might help.

Is the fresh water vent clogged or is there something else going on?
if so, what have owners done to fix the situation?

All suggestions, insights and comments are welcome.

Thanks!
Roy

Fin Fisk
Lake Pepin (Mississippi River)
Pepin, WI

 

[Osprey]

When you put air pressure on the vent line you were likely trying to add air to a closed system. This would make it appear that the vent line was plugged. However, this test method would be okay If the fill hose connects near the top of the tank and if the fill cap was off i.e., no longer a closed system.
An easier test is to overfill the tank with water. If the overflow escapes from the deck mounted fill fitting, then the vent is plugged. On the other hand, if water escaped out from the hull mounted vent port, then the vent is not plugged.

It might be possible to carefully feed a steel fish snake down the vent line. This would clear a simple debris plug. I think a pinched (kinked) hose is unlikely given that the tug is a 2012 model. Such a problem would have shown up may years ago.

Gaining access to the tank connections is not easy. You would have to install an access port in the floor. Where in the floor? You are going to need help from the factory to determine the best location.

 

[royf]

It's possible the problem has existed for a while. The survey didn't check the system thoroughly (the pump pumped, antifreeze flowed, check).

I did have the fill cap off during my air pressure test. My assistant didn't hear any bubbles or gurgling sounds at the filler pipe. Unless something got in the tank it's not clear to me what could clog the vent. Running a stiff wire sounds reasonable though if there's a right angle fitting at the tank it may not clear it.

It's possible access may be available by cutting the interior cabinet walls inside the fridge compartment rather than the floor.

Thanks for your help!
Roy