2002 H260: is the drinking water tank vented?

[Rick Macdonald]

Does anybody know if the drinking water tank on the 2002 H260 is vented?

On my buddy's H260, the galley and head sink pumps (Whale Flipper Galley Pump GP0418, non-pressurized) lose their prime and the water drains from the lines back to the tank. This doesn't happen when the tank is full, but starts when it's about half full.

The "suction" felt if you put a finger over the faucet hole is quite strong. It will even pull the pump handle from one end to the other depending on where you leave it positioned. Within seconds it drains enough that you have to pump many times to get the water back to flowing again.

It doesn't seem to me that gravity / hydrostatic pressure would be enough to do this. The only thing that I've thought of so far is the the tank is not vented, completely airtight at the filler on the deck, and the vacuum in the tank increases the more water that's pumped out.

I've ordered a couple of non-return check valves from Whale (FV1227). I thought they should go close to the pumps but a fellow at Whale in the UK said to put one close to the tank between the tank and the Y-piece that splits the tube to go to the two sinks. Or if not enough space there, put one on each line just past the Y-piece.

The boat is about 90 minutes away but we'll be going up to work on it next week (preparing for 2 weeks in the US San Juan Islands (WA state) a couple of weeks from now).

Any ideas about any of this?

 

[Ron20324]

You should have posted this question BEFORE you bought parts that probably not fix the true problem. You should have access to the top of the tank to see where the vent goes. If you fill the tank from the deck, water would probably backflow out the vent when it is coming back up the filler fitting. Mine does, as the vent is lower than the deck.

 

[Rick Macdonald]

Ron, I'm not sure what your point is. Are you saying the tank is vented but our vent might be blocked?

 

[thinwater]

Ron, I'm not sure what your point is. Are you saying the tank is vented but our vent might be blocked?

Yes. Mud wasps love the hoses.

Also consider adding a strainer to the vent. I've found bugs in the tank, and the land plumbing code requires 20-mesh screens on all potable water tank vents. Don't know why boats skip this.

 

[kloudie1]

and part B.. the hand pumps have a non return valve in the base which allows them to work.. sometimes they get a little fouled up and will leak.. they are not hard to disassemble and clean.. usually you can pull the hose and unscrew the bottom and then easily clean the ball(s) and seat(s) .. This in conjunction with opening the vent should fix ya.

 

[Peggie Hall HeadMistress]

Does anybody know if the drinking water tank on the 2002 H260 is vented?

ALL tanks--water, fuel, and waste--MUST be vented because the vents have two main functions: to provide an escape for air displaced by incoming contents (otherwise the tank becomes pressurized), and provide source of air to replace contents as they're drawn out.
You're able to completely fill the tank only because hose doesn't completely seal the deck fill...air can get out of the tank around it while the tank is filling. And there's always some air above the surface, which is why you're able to draw water out when the tank is full. But as you draw more water out, the pump starts to pull a vacuum. That suction you're feeling at the faucet is the pump desperately trying to pull in some air through it.

The solution: first determined whether the tank does have a vent..it'll be a 1/2" hose fitting on or at the top of the tank that should have a hose attached that should run to a thru-hull on the side of the boat just below the toe rail. If there is, that thru-hull may be blocked by a mud dauber nest...very common this time of year. If there is no vent fitting on the tank, you'll have to install one, but it's actually pretty easy to do...we'll cross that bridge if we have to.

If you don't have time to do any of this before you leave on your cruise, you can temporarily relieve the problem by opening the deck fill cap each time you need to run water. A bit of PITA that'll require planning when to run water, but at least you'll be able to go AND have running water.

 

[twalker H260]

Our 260 the pumps worked the first year or two, put in check valves, rebuilt and had them work for another year or so. Eventually just put in a powered pump no further problems - makes draining and winterizing much easier. Our vent is located port side, forward under the anchor locker. When filling water will eventually flow out the vent.

 

[Benny17441]

Should be, otherwise the flow of water in and out of the tank would be impeded.

 

[Rick Macdonald]

Thanks everyone for the interest and ideas. I was wrong. The vent is not blocked and the symptoms are as described even with the deck filler cap off.

That leaves hydrostatic and siphon effects. The pumps are of course higher than the water level in the tank. It still makes sense that the loss of prime is minimal or none when the tank is full and gets bad and worse as the tank gets to half full or less.

It would have been too difficult to insert check valve(s) right at the tank even if we had the parts to make the connections so I put one under each pump (head and galley).

It's not perfect but the loss of prime all the way back to the tank takes an hour or three instead of seconds. We're happy with that.