Water tank air release valve

[Johny London]

And so onto the next thing...

I have a small amount of water in the bilge up by the water tank, and I have reason to suspect that it has come from the air release valve on the tank, which can be heard burbling away at times. It is mounted to vent the air inside the boat, which I'm not sure is a good idea, because on one occasion, when I had a hose end attachment that happened to sit in the water filler hole quite snugly. water definitely overflowed from the air valve and came in the boat. Since then I have been careful, using just a loose hose end when filling - in order to avoid any pressure build up. Though - I have seen other boats that seem to have a lock in hose filler end, so presume they have a different type of valve for air release, or something. Anyway, as I said, it's a little wet in there now (under the tank which is a stainless steel one) and I think it's prolly just due to that stupid air valve, no sign of leaks.

 

I wonder if anyone can offer advice - for example should I route the air release to outside the boat, is it just faulty or is there a different/better way of doing things (even permitting a tightly connected hose when filling?).

[system 4-50]

I have a Hozelock snap connector piped to a 12V valve controlled by a Teensy (Arduino type thingy) and a Wema tank level sensor to the tank(s) with an air pipe (15mm)  to over-the-side. So far the air pipe has never filled with water which is good as I'm not sure my tank lid is watertight.

[Johny London]

Ah, I suspected as much - I may have to pipe the air vent to outside the boat. 

Are you saying that with the Ardino thing it switches off the water at a certain pressure? I don't want to go that elaborate - just a dry bilge would be enough. Presumably in my case I can then (once air pipe routed to exterior) happily let the air release valve splosh out water until I turn it off.

[system 4-50]

12 minutes ago, Johny London said:

Ah, I suspected as much - I may have to pipe the air vent to outside the boat. 

Are you saying that with the Ardino thing it switches off the water at a certain pressure? I don't want to go that elaborate - just a dry bilge would be enough. Presumably in my case I can then (once air pipe routed to exterior) happily let the air release valve splosh out water until I turn it off.

Yes, that I believe is what most people do.

The Ard just uses the level sensor ( a float type), not pressure.  It also switches to the 2nd tank when the 1st is full, and shows the level in all 3 tanks (3rd is PO) on a 2.8" TFT screen. And it can  via a speaker announce the time to full at 1 min intervals.  All just for fun.

[ditchcrawler]

Are we talking cold water storage or Hot water cylinder here?

 

[Johny London]

Cold water storage.

[Boater Sam]

If you take it overboard, fit a spider proof gauze, in fact always do this, else you will have a community of bugs in the tank.

[Tony Brooks]

And a swan neck unless it exits very high up the boat, you don't want tideway water getting into the breather when you go through a wash.

[Johny London]

Surely the whole point of having a valve is that it allows things to go only one way? Though I think in practice, the advice is good!

I can't see the valve, only hear it. Unfortunately it is at the side of the tank, and will require removal of half the boat to get at it.

[Tony Brooks]

The vent should be on top, not the side but in any case the KIS principle suggests the valve is an unnecessary complication for a tank breather on an inland boat. Different if the boat was desined to potentially submerge or roll right over.

[Johny London]

So, with no tank breather, air can escape by the fill hole when filling as long as the hose is a loose fit and not "coupled" in some way, but what would happen when using the tap later? Surely a vacuum would be created and soon the water would be unable to be pumped? Mind you - that means what I thought was an air escape valve might be designed the other way around! (thumbs up for the bug guards!)

To add to my confusion, I see nothing on the top of the tank, and indeed cannot actually see anything of the air valve.

[Tony Brooks]

1 hour ago, Johny London said:

So, with no tank breather, air can escape by the fill hole when filling as long as the hose is a loose fit and not "coupled" in some way, but what would happen when using the tap later? Surely a vacuum would be created and soon the water would be unable to be pumped? Mind you - that means what I thought was an air escape valve might be designed the other way around! (thumbs up for the bug guards!)

To add to my confusion, I see nothing on the top of the tank, and indeed cannot actually see anything of the air valve.

Exactly. Vents on water and fuel tanks need to pass air in both directions depending upon filling or emptying and you can not be sure from boat to boat that the filler pipe is flush with the top of the tank. If its not you tend to build up a pad of pressurised air this then blows water back out of the filler so its better to have the vet from the top of the tank. I have never heard of an air valve on a water or fuel tank but can believe thy may be fitted on the odd specialised boat. For normal boats I think they are just a complication.

 

Anyone else got more info on this valve?

[Opener]

I've got a very simple setup.  The fresh water tank comprises the sides and base plate of the bow plus the foredeck and a bulkhead to the rear.  Hole in the lower rear face with a tap fitted linked to the pump and water system.  Filled through a hole in the foredeck - hose fits loosely.  The filler inlet is "sealed" with a screw cap which looks a bit like the filler on the diesel tank ie dead simple.  It can get a bit tight so it has a horizontal tube welded across the top face which will take a tommy bar/screwdriver/poker.  Look at this carefully and there is a drilling through the top of the screw cap which communicates with the bore of the tube.  Not exactly a 'valve' but it does relieve any vacuum which may form when using water or any pressure which may build up from the intense heat of the English Summer!  Not spider proof but there is a filter before the pump - haven't found any corpses in there yet....

[Johny London]

I sometimes wish my tank was integral. I presume you have a nice big inspection hatch bolted down on the well deck too - so you can really get at it to inspect and clean. 

Still, I have what I have and will have to work with it. Either way (be it the air valve is for admittance or release) it seems it can spill water into the boat if not very careful. However, it occurs to me that the water this time could be from condensation - I certainly haven't let the hose get jammed in blocking the filler hole, and I rarely turn the fill tap on all the way, plus I make sure to turn off the minute it starts overflowing when full.

Bottom line I could do with accessing that valve but it will be the job from hell - a bookcase to remove (plus contents) pus the ply wall of the boat, by the door.

[Detling]

The water under the tank may well have come from condensation on the outside of the tank running down. At this time of year the air is moist and gets warmed a bit by the sun, hits the nice cold tank and hey presto you get condensation.

[Johny London]

I think I'm gonna file this one on the back burner! If ever I get the side of the boat apart I'll be sure to look at the air vent. Thanks for the help.