Fresh water tank

Fresh/Waste Water Systems, Watermakers, HVAC, Refrigeration...
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mike cunningham
Posts: 489
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Fresh water tank

Post by mike cunningham »

OK smart people, I have a mystery wrapped in an enigma. When I fill my water tank (standard F30 plastic under stbd settee) as the tank fills to about 2/3 full it begins to develop pressure, a lot of pressure, enough to begin ripping screws out of the over tank cover and the front of the settee base. I realize there is an overflow tube in the upper part of the tank and I am able to blow back through this when the pressurization begins but I do not get the expected flow from the tube. I am obviously missing some basic science related to air and water pressures. Help!!
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

AlanK
Posts: 127
Joined: Wed Dec 10, 2008 6:59 pm
Location: Freedom 33 Boston, MA USA

Re: Fresh water tank

Post by AlanK »

If I understand correctly and water is not coming out the vent line with al that pressure then the line must be clogged. Manuually blowing into it you probably can't tell because of the length of the tubing ad volume of air you would need to really check it. You could try an air compressor. Or just run a wire through it.

Mike Holibar
Posts: 174
Joined: Mon Jun 01, 2009 12:41 am

Re: Fresh water tank

Post by Mike Holibar »

Mike,
the vent line must be clogged or restricted. If you use compressed air to blow down it, make sure your filler cap is removed and taps on to relieve any pressure in the tank. Even a small amount of pressure can do a lot of damage as you have seen. It may also be that the vent is too small for the rate at which the tank is being filled. I remember years ago filling a new tank I had fitted in an old launch. I had from memory something like a 1 1/4" fill line and two 2 3/8 to 1/2" vents. I reasoned (in error as it turned out) that air would flow out more easily than the diesel would flow in. Once the tank was about half full there was enough pressure to force the fuel back up the fill line, making an awful mess. as I stopped pumping I could hear the air hissing out of the vent lines. The answer in this case was to fill the tank more slowly to allow the vents to relieve the pressure.

Regards,
Mike Holibar
S/V Fyne Spirit of Plymouth (Freedom 39PHS-1989)
Lyttelton
New Zealand

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Michel
Posts: 546
Joined: Sun Dec 07, 2008 5:48 am
Location: Zaanstad, the Netherlands, EU

Re: Fresh water tank

Post by Michel »

Mike, you might want to check if your tank vent hose doesn't extend too low inside the tank. If it is, you can blow back air into the tank, but air cannot escape when the tank is filled. Perhaps the longitudinal trim of your boat is different now, so that the vent is not at the highest point in the tank anymore.
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

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mike cunningham
Posts: 489
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: Fresh water tank

Post by mike cunningham »

Thank for the ideas, suggestions everyone. I will go down to the boat a get serious about investigating clogs and location of vent. Freedom Yachts, of course, made it a diabolical effort to view all the tank gozintas and gozoutas. Things are very tight all around the tank and its hard as heck to see the business end of the tank which is butted up against the aft settee/chart table bulkhead.
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

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rvivian
Posts: 210
Joined: Sun Feb 21, 2010 2:08 pm

Re: Fresh water tank

Post by rvivian »

Mike -

I'm redoing the plumbing on my F-30 now.

I took a hole saw and made a 4" hole in that bulkhead to get at the plumbing connections and re-route the outlet. Then I coated the cut wood edges with epoxy and covered the hole with a SS louver.

My vent goes up behind the electrical panel and then is routed back down alongside the water tank to vent into the bilge. I'd like to figure out a way to vent it into the galley sink (of course it is on the other side of the boat.
Heart's Desire
Freedom 30
Shelton, WA

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