Re: [Amel Yacht Owners] Minor flood

James Alton


   I think that you are making a very important point.   If the tank were accidentally pressurized to only 10 PSI  (City water pressure I believe is usually around 40, so this would actually be easy to do) and we assume that the tank top is roughly 24 square feet in area, the force acting to “blow the lid” would be more than the designed weight of the boat…  A warning label at the tank fill might not be a bad idea??

    I have noticed on our boat that the tank fill pipe ID is pretty close to the OD of a normal water hose male end so it would not be hard to have it jam in the hole and that could be bad.  I was thinking of always using a short section of hose screwed on to the male hose end so that only the smaller hose would be in the fill pipe which would prevent pressurization of the tank.   

   The air vent will not give you much protection once the vent line was also filled with water when the tank is overfilled,  especially if the fill rate is rapid.  I  doubt that the access plate seals would go before the bond between the tank top and the hull.  Perhaps there is a built in relief valve somewhere in the system but I have not seen it anywhere on my tanks or in the plumbing so as you point out, careful filling procedures might be the only protection.


James Alton
SV Sueno,  Maramu #220
Arbatax,  Italy



On Nov 21, 2016, at 5:59 PM, Bill Kinney greatketch@... [amelyachtowners] <amelyachtowners@...> wrote:

Another thought on water tanks that people with lots of years on boats will know through their own, or someone else’s, painful experience:  When filling a water tank do NOT jam the water hose down the fill pipe and turn it on at a high flow rate.  

It is possible for water to go into the tank faster than air can vent.  It takes very little over-pressure before access hatches and such blow their seals. They are not designed as pressure vessels!  The resulting leak can be either catastrophic, or subtle and hard to find. In the case of boats built without integral tanks, failure of an entire tank seam can occur.  

Do not try to fill any tank faster than the liquid can go down the fill pipe by gravity. Patience is a virtue!

Bill Kinney
SM #160, Harmonie
On the Hard, Fort Lauderdale, FL
“Ships and men rot in port."

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