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post #1 of 13 Old 10-26-2009 Thread Starter
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Water Tanks

The aft water tank on my 34 1989 Pacific Seacraft needs to have the plywood lid replaced. One of the inspection ports developed a leak, that allowed water to seep into the plywood, causing it to delaminate. My current plan is to cut another plywood lid, and coat it with fiberglass resin to waterproof it. On the old lid, the inspection ports were never screwed down, they were simply glued into place using silicone. My question is why did Pacific Seacraft choose not to screw them into place. Is there a safety reason for doing this, i.e. they want it to be the weakest link in case the vent tube is blocked, or the tank freezes. Any thoughts?
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post #2 of 13 Old 10-26-2009
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May I suggest that instead of plywood you use the grey plastic/pvc lids that PSC switched over to just after your boat was built? They do not have the same maintenance problems as the old plywood lids, and once you've cut them to size there is no further step of coating them, etc.

I don't know why your tank lid lacks screws. On our 31, the plastic tank lids are bedded with silicone and screwed down.

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post #3 of 13 Old 10-26-2009
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On my 1997 PSC 34, the grey plastic/pvc tank lids are also bedded with silicone and screwed down. In really rough going, I'd want the lids screwed on.
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post #4 of 13 Old 10-26-2009
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I'd vote for the PVC as well. I used it to replace the plywood top on my holding tank. The job is described in a post dated 8/16/09. Both of my water tanks already had gray plastic tops. Clear inspection ports are nice too; you can look into the tank. It is almost as good as a level gauge.

Bill Murdoch
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1988 PSC 34
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post #5 of 13 Old 10-26-2009
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I replaced my leaking plywood aft water tank lid with a gray PVC one according to the excellent instructions I found on this site. I added 2 inspection ports with silicone bedding and screws. Can't imagine not using screws. The PVC is quite a bit heavier than plywood, but otherwise I see no disadvantage (other than cost), and it gives peace of mind.

Paul Cooper
PSC31 #9 "Wayfarer"

The secret to sailing is good judgment. Good judgment comes from experience. Experience comes from bad judgment.
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post #6 of 13 Old 10-26-2009
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Do I understand right that the lids of both water tanks of a 1983 vintage 37 are likely to be plywood?

I'm wondering if perhaps this is the source of a leak into the V berth - it's not coming from outside (at least, I can't find it) but maybe from underneath the mattress? (This would be an easily solved problem...)

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post #7 of 13 Old 10-26-2009
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Dear Bill, our aft water tank was wet on top and, after a deluge, I concluded that the water was coming from the tank, not the outside. I went around each screw hand torquing them down and figuring that the silicone would form a nice gasket. Some of the screwes were quite loose and doing so solved the wet berth problem entirely!

Jay, PSC 37 # 171, Kenlanu
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post #8 of 13 Old 10-27-2009
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Leaks from water tank inspection ports

Our 1983 PSC 37 (hull #42) had plywood covers for the water tanks; the plywood was laminated to white Formica (or Formica-like material) which was installed so that the Formica faced the interior of the tank. The inspection ports were screwed down and bedded. We never had a leak from the inspection port. What we did have--and it's only related because it involves the water tank--were blisters. That's another thread.

Our 2006 PSC 40 also has white formica-lined plywood tops for the water tanks, with the inspection ports screwed down and bedded. We swapped out the original inspection ports for larger ones to make cleaning the tank easier. The new ones are torqued down around the outside (the opening part itself is a screw-on fitting) and bedded with silicon sealant.

Despite all that care, we failed to screw down the lid on the port completely during an offshore passage, and wound up with 1/2" of water on the bed platform. Only the Frohli springs kept the mattress from being soaked, too.

Our lesson is that no matter how carefully you install, it will leak if you don't screw it down properly. We've had no leaks since.
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post #9 of 13 Old 10-27-2009
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Our 2000 PSC37 has clear inspection ports screwed down, but wanting to be able to open her up for cleaning at least once a season, I replaced the silicone bedding with silicone sheet stock from McMaster. It's been water tight.

Unomio mentions the Froli system and it looks really nice, but it's pretty pricey. I had some leftover "Cedar Breather" underlayment (link here) from the time I did a cedar shingle roof that I put under the mattress and while not nearly as effective as the Froli system, it was "free" for me as I had it laying around.

s/v Little Wing
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post #10 of 13 Old 10-29-2009
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I have an 1983 vintage 37 with the plywood lids.
I have had leaks from the inspection ports, and I went in search of the rubber seals for the screw in deck plates (I thought they were "O" rings, but they are actually triangle cross section and referred to as "gaskets" by the manufacturer). My deck plates are made be Beckson.
On the Beckson web site I found the gaskets, but I also found their clearance section where they had the whole deck plate for not much more than the gasket. So I bought 4 new deck plates and I intend to replace the existing ones and add an extra one in each tank to aid cleaning.
The last time I checked, the plywood seemed to be in good shape. The screws that hold down the lid in the V berth, are partially cover by the interior cabinetry, so I don't know how you get them out?
The other problem I have had is when both tanks are full. The bow tank is higher than the stern tank, so if you turn them both on the water drains toward the stern tank and fills it, then applies static pressure to the seals which causes them to leak. Now I make sure only one tank is turned on at a time.

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