Water tank vent problems

I have a CSY37 and the Fiber glass water tanks swell up like a Balloon when I fill then to full. There is a 3/4"vent overflow about two inched from the top of the tank on the forward side next to the Fill but no water comes out until they are completely filled but at that point they start to Balloon and it is causing all kinds of stress problems / leaks etc. I think I need to move the Vent higher but can't put it out of the top because there is no room. it seems that there is a Air pocket at the top causing this problem! Should I put a vented loop in ? but I don’t see how that would solve the problem! Any body with any Ideas would be most appreciated???

 

Welcome to the forum Stuart,

That would suggest the tank is not stiff enough to hold the hydrostatic pressure.

Since:

That is what the vent is for, for over flow.

 

If the vent outlet is below where it is connected to the tank, and the tank is full, how do you explain nothing coming out of it ? It doesn't make any sense, unless the hose be blocked.

 

Can you access an area say 2 inches around all of the tanks? Send some pictures of the the outside perimeters of the tanks, all around. It may be relatively easy to build an external bracing system in place if you have access.
A couple of ways would be a built to shape set of clamps, pulled together with stainless ready rod. If the tanks are round, a simple strapping system may work. If the tanks are removable, you could probably just fibreglass in some external
ribs.

I would expect that there is a forum for the CSY37 and if the tanks are an issue, someone may have come up with a solution. Depending on the size of the tanks, perhaps they may have had some baffles installed during construction that
have released from the side.

CruisersForum you could post in there to see if anyone has had similar issues

 

Most likely the vent line is clogged. Stick a waterline on it and turn it on and see. Vents often get mud daubers filling them; so verify the vent is a vent.

 

Stuart, which layout does your CSY have?
Attached below are copies of a catalogue I have for her.
I know a CSY 37 here called Islander; she has the Plan A arrangement. Her water tanks were under the settees in the saloon (she has recently had new fibreglass water tanks installed as part of a major re-fit).

 

A clogged vent will not increase the pressure in the tank when it is getting filled, since the fill pipe is open to the atmosphere. The pressure is a function of the height of the water above the bottom of the tank. If you put a vent hose that ends higher, the pressure will increase. Air bubbles at the top of the tank will not increase the pressure.

 

Good point. The only way the vent has anything to do with it is if the fill side is under pressure which shoud not be the case.

the likely story is the water tanks are shot