Building a head tank

[Irwin32]

Opinions: I am thinking of getting rid of my porta potti and installing a holding tank. Under the V berth was once 40 gallons of water tankage that a previous owner opened up for storage. The old tank is actually an integral part of the molded pan for for the interior of the boat. Under the V birth they molded the pan into a deep v tank and then covered the top flat, where the cushions sit upon, with 1/2 plywood that had the tankside surface laminated. Opening up the plywood top, one sees a V shaped tank, wider aft and getting narrower and shallower forward. The interior of the tank is the same gel coating used throughout the cabin pan. I am thinking of using 20 gallons or so of of this tank as my new holding tank. I would fit a piece of glass sheathed plywood as a wall, and glass it solidly to the inside of the old tank, which would now be part holding tank and part storage. I have not yet thought out the cover - though either glassing it on, or making it removable w/gasket and lots of screws is a possibility. Holding tank modifications are serious stuff and one does not want a shoddy plan. Any thoughts?

[pirateofcapeann]

Just a thought. I had the same configuration in my C22 but the tank was only 20 gallons. I actually hacked out the tank and opened up a heck of a lot more storage space up there. You may be able to put in a holding tank with out loosing any storage space at all! Look long and hard at it first because putting the tank back in may not be an option.

[jklewissf]

Before I went to all the trouble of fabricating the wall and top for the existing tank I would check for rotomolded polyethelene tanks that might fit the space and have the fittings already installed. I did this on a boat about 10 years ago. Fortunately the guy in the marine store told me that there are a lot more sizes of prefab tanks available than what you see on the shelf. After 5 minutes with his catalog I found the perfect tank and the manufacturer was even willing to install the ports where they would be easy for me to do the plumbing. Total cost of the tank was less that $80.

A couple more suggestions that you might find helpful.

Don''t use cheap hose. Get the white kind that needs to be heated before it will slip on the hose barbs. After 10 years my holding system does not stink.

If you dont have a very big tank you might consider getting a lavac head (defender sells them) They are not cheap but they use a lot less water per flush than the more common marine toilets. They are also extermely simple in design. I used mine a lot for 10 years and never had to rebuild the pump.

Hope this helps.

John

[tsenator]

Why not just buy a tank that can fit in the space. A holding tank has to be *completely* enclosed with no possible leaks no matter how small or microscopic. If you don''t, the holding tank will leak & smell with permiate the boat. I don''t recommend it. Ronco makes a lot of different sizes and shapes that are reasonably priced and made for holding tank purposes.

Take a look at http://www.ronco-plastics.com/

Also remember to ude the best marine sanitation hoses on the market or the "smell" will permiate the hoses quickly.


Also review the Head Mistress (Peggy Hall) she has spent a career in Marine Sanitation take a look at http://boatsafe.com/nauticalknowhow/phall.htm

[Irwin32]

The Ronco site looks like a good bet. I will have to measure my space to see if the make a tank that will fit - or at least be close. I was unaware that so many different tank configurations were available. I had only checked with West, boat Us, etc. thanks for the lead. Dropping something into the space would certainly be easier.

[roline]

I do not recommend fiberglassing in the holding tank. The Hunter 28.5 has the holding tank glassed in under the rear area and the one in our club had a nasty odor that could be detected from the dock when you walked by. My Cal 9.2 had a bladder holding tank and I do not recomment that method, same issue odor. I could not find a tank that I liked so I ended up custom fabricating one from 12 layers of glass and epoxy. It is 3/8 to 1/2" thick and is removable if needed. I would have prefered HDPE. Use the expensive white solid reinforced vinyl hose with short runs to the tank. My tank is behind the head so when flushing, the transfer hose can be flushed with a few extra pumps to be sure it will only have flush water sitting in it.

[sailingdog]

The best hose to use is supposedly the OdorSafe hose, which is highly recommended by Peggie Hall.