Printable View
So I have a bit of a problem. I removed the under berth tank in the aft cabin and vented it out the same port as before. Filled the tank yesterday only to find the master cabin floor swelled up by a bloated water tank below.
Any idea why this would happen?
Could this be from excess pressure on my keel being as the boat is laid up transfering to the full water tank?
Just want to make sure I don't blow a hose or worse yet, rupture the tank!
sounds like you filled the tank too fast, and pulled the screws out that hold the top of the tank to the baffles. this happened on my 46c. bigbill
This also happened on my 55C. Major design flaw. We have ruptured the top of the tanks a few times. We have tried everything, increasing the vent size,etc. The tank won't vent when full. Design flaw!!! Can't seem to fix the problem, When the bilge pump goes off the tank is full.
Mike
"Habanero"55C
Ditto for my water tank. my solution; abandon the vent line and simply place a short hose lenght from overflow fitting into closest bilge. I've had no problems ever since and you can fill tank until you 'get around' to shutting of the water because the overflow fitting will out put as much water as you can put into it with a typical 5/8 hose. I agree that its a design flaw but hatts have so few I'm not complaining! now if it were an Ocean...
I have heard that if you always fill from the OEM deck fitting that you will never hurt the tank. The problems occur when someone installs a "back fill" from the pressure water system to fill the tank through the normal outlet that goes to the pump. Has anyone else heard this?
I haven't heard that, but i am using the OEM fill. Like the overflow idea, but doing that will simply fill the lower tank. The tank behind the bed in the main cabin sits 3 feet higher and will drain out the overflow. Therein is your reason for having the vent be higher than 3 feet.
The pressure in the lower tank is just too high. There is no way to relieve it except draining some water from the higher tank. Seems crazy this is the case!
Is your tank foamed in place...with just the top to expand due to excess pressure? if so maybe you can build a 'ladder' type brace to fit over the top of the tank to contain the expansion. or is there no room?
You know you got me thinking. The previous owner replaced the deck above the tank. I bet he didn't put as much bracing as the original design had. I'm going to tear it up and see if I can reinforce it. Thanks for the suggestion!
Forget that idea. I think I have a more elegant solution to the problem. The hose connecting the high and low tank is 1.5". My guess is, this allows a good deal of pressure to be transferred from the higher tank to the lower.
Solution: create a bottleneck in the 1.5" hose. Splicing in a 1.5" to 3/4" back to 1.5" in the aft bilge should restrict the flow and hopefully help with the pressure build up.
Or if you think I have a poor understanding of fluid mechanics, please educate me. :-D
That's not going to change the pressure. You'll still have the water above creating the pressure. You could, however, add a valve to that line and just open it when the lower tank empties.