Plumbing question: head to holding tank

[ChrisS]

I'm getting ready to dismantle the current head and holding tank setup this week to clean and paint the bilges, and then rebuild the system. It must be at least 25 years old, and is due for replacement.

There is a Y valve with direct discharge or to the tank; the tank is located under the seat aft of the main bulkhead. For the waste to get to the tank, it must go up a "riser" of sorts to the Y valve, and then it falls to the tank. (Interestingly, to fit the space, the tank is tilted inboard--because the outlet is on the outboard side, I don't think the tank is ever more than 75% empty--nasty!)

Is this riser necessary? I surmise that it is there to keep waste from flowing from the tank back to the head when the boat heels, but for the waste to get over the riser, a vigorous flush is needed, filling up the tank quickly.

Does anyone have any wisdom on this? I'd also appreciate any other plumbing tips people are willing to share.

 

[Glyn Judson]

Chris, Do consider a slightly modified version of the West Marine "Our Favorite Method" that can be found on Page 506 of their 2008 catalog. This system routs head waste directly to the holding for overboard or deck discharge. I've installed a number of these using the identical design but exception of the Y-valve shown as #8. Look at it for a moment and you'll see for yourself that a valve is not needed at all and just adds to the confusion of use, especially for someone not familiar with how it all works. I have the identical setup in our boat, the second for me to install in our last two boats. We have a macerator and discharge off shore is accomplished by simply opening the seacock and depressing the pushbutton switch. When back home, I use the deck fitting at the pump out dock. It's important to flush an empty tank several times with fresh or sea water several times before the job is done. I use and highly recommend ODORLOS head treatment as a simple, very affordable and effective means of ridding any and all head odors permanently. Glyn Judson, E31 hull #55, Marina del Rey CA

 

[ChrisS]

Glyn, I'm with you on the rinsing and Ordorlos technique, and I haven't decided if I am going to have the Y valve or follow the WM diagram (I have two daughters and the head gets a lot of use). I was going to use a manual pump for the discharge due to the fact that I wouldn't have to wire anything, but it all depends on space limitations. I am going to rip the whole system out tomorrow and start planning.

If I don't have the "riser" and keep the head to tank line sloping from the head down to the tank, will I run the risk of backflow from the tank to the head when the boat heels? I really want to get this job done right with no unpleasant surpises.

As a sidenote, right now I have a 9 gallon Kracor tank, with a disabled recirculating system. I think the best I can do in the same space is an 11 gallon Ronco model. I really wanted to shift the tank location to the vee berth locker just forward of the head, but I would then cover the speedo thru hull, and I think that's not a wise move to make.

 

[rwthomas1]

Heres how it is in my E38: The head discharges to the holding tank. The holding tank has three large hose barbs, one for the inlet from the head and then one for deck pumpout and the other to a Whale pump and then a seacock for pumping out offshore. It works very well, there are no unnecessary valves, etc. The only negatives I see are the potential for waste to sit in the piping from the tank to the respective outlets but that is the same with any system. The other issue is the tank-Whale-seacock hose is not run above waterline, no vented loop, etc. There is the potential that the overboard pumpout line could backflow, fill the holding tank, etc. I have not let this worry me simply because that seacock is used infrequently and the handle has been removed, per RIDEM requirements, to make it inop. The only time the seacock would be open is offshore and the tank is being pumped. There is little opportunity to forget about the open seacock in this case. RT