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As I have been slowly updating all my systems I decided to build a new holding tank, above the waterline. The old hoses needed to be replaced and were hard to reach running through the settees and bilge. In addition there was a leak in the old tank. By building a new tank I could keep all hose runs very short. The final tank holds just under 25 gallons.
Using 1/4 fiberglass stock I made the sides and a bottom of the tank. I used the hull to form the back of the tank.
I made the top and front out of the same 1/4 fiberglass panel.
Put the tank back in place and hooked up all the plumbing.
Beautiful! Errrr...did I say that about a holding tank? Seriously- looks great!
Rich W.
s/v CARAL (a tribute to Carl Alberg)
CD Typhoon #995 (useable project boat) (sold)
s/v Sadie
CD Typhoon #858
s/v Azure Leizure
IP 350 #120
Tiverton, RI
...above WHICH water line
on our little 27 the ships' waterline and the head's "waterline" were about equal. A full holding tank would have challenged gravity
Last edited by tjr818 on Sep 16th, '15, 09:30, edited 1 time in total.
Yikes! I hope this arrangement works out. The rim of the head on Raven is about a half inch above the waterline. I flooded it one time in very calm conditions to determine this fact.
I know the head will move it's contents up hill. It does this on Raven when I have the Y valve set for overboard discharge. It must pump up to the anti siphon valve on it's way to the seacock. There is always some backwash. With the overboard discharge, it isn't a huge issue as you can keep pumping a lot of seawater through the system until everything is clear. It does drain everything back from the high point back into the bowl and you can never pump it out completely. This is a minor annoyance to have some water sloshing around in the bowl. I forget if there is a check valve in the discharge line and it might be that mine is leaking to create this situation. Even if there is, it would mean that the sanitary line to the holding tank is always full. I know some boats have high holding tanks so it must work out okay.
Never the less, I feel that gravity is your friend when dealing with these matters, Steve.
Yes, if my joker valve fails there is the potential for the contents of the hose between the tank and bowl to back-flow into the bowl. The bowl is large enough to hold this volume without overflowing, if we are not heeling too much. I have not yet calculated the number of pumps needed to make sure solid waste is out of the hose but I plan to.
My original setup had quite a few things I disliked as well. My loop was too low in the boat. It should be higher than the waterline at whatever angle of heel you are sailing at. That means using a bunch of hose to bring the loop towards midships, having it pretty high anyway or closing the seacock on port tack. The check-valves in the top of the loop can corrode, making it functionally useless, something else to check (very few of us ever do). There was nearly 10 times as much hose. And the only way to empty the tank was to pump it out. The onboard pump is very rarely used (electric or hand) I questioned how reliable it would be when I did need to use it.
