Fresh water tank vent - geometrical problem - vent to bilge an option?

[Fredct]

I have fresh water tank inside locker. Fills from top, drains from bottom. Vents from top side.

Because of size of locker, vent line runs horizontal then dips before making its way to the thru-hull vent hole. I cannot make the entire line go straight up from tank (like it should).

Problem is that when heeling, water goes into the vent line and blocks it. Pump has to work very hard for very little flow.

I am showing problem area with RED arrow.

Is there a way to plumb differently? I thought of connecting fill and vent with a valve in between or connect vent line to bilge (again using a valve)...

 

[capta]

If it vents on the side of the hull, I would have a big loop up to the deck to keep the seawater out.
And yes, replumbing will be necessary, and probably to a new vent. The air flow must be unencumbered to function properly.

 

[rgranger]

I'm currious as to why you would need to vent a fresh water tank over the side of the boat in the first place. Why not put a one-way check valve here to keep water from spilling out ...

They make a lot of different types but something like this should do the trick

 

[Fredct]

Fresh water gets into the vent line from heeling, it is not seawater. A vent needs to work in both directions, for filling and emptying.

 

[Capt jgw]

Saw one where they ran the tank vent to the head sink. All inside the boat so no chance of sea water getting in the line. When the tank gets full the overflow flows into the sink so no spills. Or you can run the vent to the highest point inside the boat. Also no chance for sea water but if you fill too fast it will flow out the vent into the cabin. I had one like that, worked well unless I cranked the hose faucet up too high. Many boats have the water tank vents inside, it is considered safer. Maybe you can make this work for you.

 

[Fredct]

I forgot to add that the fill line also flows below the tank so it's always full of water. Venting to sink is option on the one tank but very difficult on tank #2. They located port and starboard, both vent through similar geometrical setup that prevents a straight up run.

 

[WayneH]

The tanks on my 1980 Tartan vent up inside of the hull before u-turning to end up in the bilge. It's a clear hose so you can see all the mold inside.

 

[TimFromLI]

Put a T at the lowest point of the vent line and run it to the bilge. The overflow will run to the bilge and the existing vent will work as a siphon break so you don't suck bilge water back into your tank. The only problem is that you won't know when your done filling your tank cause the overflow will be going into your bilge. Other wise install a second vent line and put check valves in both. One to let air out and one to let air in.

 

[Benny17441]

can you add a 2nd vent that when one is filled with water the other would be free of it.

 

[Ron20324]

Put a 90-degree elbow outside the tank to point up. Put a hose straight then to amidships or where you can get it as high as you can. That should suffice until Peggy comes back

 

[sailme88]

My O'28 had the water tank under the stbd side interior settee. The pressure pump was forward under the head sink base. The vent line also ran forward and vented thru the hull behind the head's sliding mirror .

 

[Davidasailor26]

My O'28 had the water tank under the stbd side interior settee. The pressure pump was forward under the head sink base. The vent line also ran forward and vented thru the hull behind the head's sliding mirror .

Same here, and we never had problems with the pump pulling water from the tank. We often had water in the vent line when filling the tank, but it seemed to work itself out fine. I wonder if there’s something else causing trouble with the OP’s pump that’s contributing to the problem.

 

[Fredct]

As it is, my boat is ODAY28. I will see about placing a small straight riser but I think I will T-off and run to bilge, perhaps with a valve to be used when filling. I guess that I could also run the same back to the tank... At any rate, thanks for your help. Will work on it this week.

 

[Fredct]

#davidsailor, there could be another issue with the pump indeed. With the vent line closed off, the pump effectively creates a vacuum in the filling tube and the small section of vent that is free. Will need to study in greater details But I think that vent lines should be free flowing at al times.

 

[Davidasailor26]

#davidsailor, there could be another issue with the pump indeed. With the vent line closed off, the pump effectively creates a vacuum in the filling tube and the small section of vent that is free. Will need to study in greater details But I think that vent lines should be free flowing at al times.

I agree that if the vent is plugged then the pump won’t be able to overcome that vacuum. But the problem you’re experiencing isn’t a true plug, it’s just some water pooling in the low spot of the vent. The pump should be able to pull that water back into the tank on its own once a vacuum starts to form in the tank. Asking the pump to do that is no different than asking it to pull water up a few inches from the tank into the pump. I wonder if the check valve integrated into the suction side of the pump may be somewhat deteriorated or jammed, preventing the pump from creating its full suction.

 

[Fredct]

I agree that if the vent is plugged then the pump won’t be able to overcome that vacuum. But the problem you’re experiencing isn’t a true plug, it’s just some water pooling in the low spot of the vent. The pump should be able to pull that water back into the tank on its own once a vacuum starts to form in the tank. Asking the pump to do that is no different than asking it to pull water up a few inches from the tank into the pump. I wonder if the check valve integrated into the suction side of the pump may be somewhat deteriorated or jammed, preventing the pump from creating its full suction.

Well the vent lines are completely filled but you may have a point. i will run a test with the lines disconnected. If that does not fix the problem, I have other issue. I did note that after heavy heeling this weekend, the water flow was quite reduced, hence this thread. But I could be dealing with a red herring.

 

[sailme88]

Water in the vent shouldn't be a problem.. Think about it.. When filling the tank, you know it's full when water spits out the vent just before the fill overflows.. As long as you have air over the tank, it will work.. You may want to check that vent to make sure a mud wasp hasn't set up house...

 

[Davidasailor26]

You may want to check that vent to make sure a mud wasp hasn't set up house...

If there is a clog in the vent hose, and the clog gets wet, then I could see that creating added resistance and not clearing itself.

 

[Peggie Hall HeadMistress]

can you add a 2nd vent that when one is filled with water the other would be free of it.

You could add a second vent, but if you can do that, why not just relocate the vent fitting to the top of the tank...which is actually fairly easy, thanks to a li'l doodad called the Uniseal UNISEAL. And as long as you're doing that, why not move the fill fitting to a location that eliminates the dip in that line too.

--Peggie

 

[Fredct]

#Peggie, I will check clearance on top of tank. Uniseal defintely an option.
#Sailme88, not sure I follow. If air does not get into the tank, the pump creates a vacuum above the water as the level goes down.