Best Practices for 2 heads to same holding tank?

[Whitebread117]

I've recently purchased an older motor yacht (1970) that was manufactured without holding tanks. I'm making a plan to install a tank for the 2 aft heads to share.

Both heads are on stbd side and share a bulkhead, the holding tank will be installed on the same side farther aft into the master stateroom. So all the plumbing will be in line fore/aft.

On our sailboat I installed Raritan Elegance heads with freshwater flush which is what I'll be using again (worth every penny), but on the sailboat it was only one head per y valve/ tank.

What is the best way to discharge 2 heads through a single y valve / holding tank(with macerator and deck pump out) setup?

Also, the tank and heads are all on the same vertical level just above the cabin sole, and the only easy plumbing route between is under the cabin sole. I assume I'll need at least 1 if not 2 vented loops which I can hide behind faux panels in each head if needed, but I'm trying to avoid wet low points as much as possible.

Thanks!

[peghall]

Both heads are on stbd side and share a bulkhead, the holding tank will be installed on the same side farther aft into the master stateroom. So all the plumbing will be in line fore/aft.

I'm not sure that's a good idea. I've scoured every source on the net trying to find out what the Raritan Elegance weighs...it's not even on the Raritan site. So I'm guessing it's at 25 lbs/toilet. Water and waste each weight 8.333 lbs/gal...you don't say what size tank you're after, so I'll use 30 gals. A full tank would weigh 250 lbs plus the weight of the tank. So including the hoses, fittings, y-valves and any overboard discharge pump, you'd be adding somewhere between 300 and 400 lbs of weight to one side of the boat...and that doesn't include the weight of anyone using either head. What do you plan to put on the other side to balance it.

What is the best way to discharge 2 heads through a single y valve / holding tank(with macerator and deck pump out) setup?

Not sure exactly what you mean... Do you want to tee two toilets into a single line going into the tank or to a thru-hull, with a y-valve to switch between 'em? Not a good plan!

If you'd like to brain storm your whole plan one-on-one, send me an email...I'll be glad to help you sort it all out.

[Whitebread117]

Thanks Peg.

For others' reference, we displace north of 30 tons, and the 20kw gen set mounted on the port side has us listing to port an inch or so.

Peg I'll send you an email, I appreciate the prompt response and offer to help.

[peghall]

Got it and replied. Glad to help!

[Scott Berg]

Peg,
you're the best!

[Mikado]

Originally Posted by Whitebread117

I've recently purchased an older motor yacht (1970) that was manufactured without holding tanks. I'm making a plan to install a tank for the 2 aft heads to share.

Both heads are on stbd side and share a bulkhead, the holding tank will be installed on the same side farther aft into the master stateroom. So all the plumbing will be in line fore/aft.

On our sailboat I installed Raritan Elegance heads with freshwater flush which is what I'll be using again (worth every penny), but on the sailboat it was only one head per y valve/ tank.

What is the best way to discharge 2 heads through a single y valve / holding tank(with macerator and deck pump out) setup?

Also, the tank and heads are all on the same vertical level just above the cabin sole, and the only easy plumbing route between is under the cabin sole. I assume I'll need at least 1 if not 2 vented loops which I can hide behind faux panels in each head if needed, but I'm trying to avoid wet low points as much as possible.

Thanks!

I'm facing the same issue on my boat, which came from Europe without a black water tank (yuk)

I installed the forward head and now would like to plumb the aft unit to the same 33 gal v-bladder style holding tank.

Please update the final solution that you and Peg arrive at. A layout sketch would be awesome if possible.

Thanks !!

Jeff

[peghall]

I installed the forward head and now would like to plumb the aft unit to the same 33 gal v-bladder style holding tank.

I can already tell you that connecting two toilets at opposite ends of a boat is a bad idea because about 6' is as far as any manual toilet can move bowl contents and except for the all china "thrones" like the Raritan Marine Elegance,the same is true of electric macerating toilets. And a bladder is not a good choice for waste holding...among other reasons they're designed to hug the contents, which makes it almost impossible to maintain the contents aerobically (the key to eliminating odor out the vent). If you've already put a bladder tank on the aft toilet, not much you can do about that now...but going with a rigid plastic tank doesn't means you're limited to a few rectangular shapes. Check out Ronco Plastics Ronco Plastics marine Tanks They make TOP quality thick-walled water and waste tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular, and they install fittings in the sizes and locations specified by the customer when they make the tank.

If you'd like my help to figure out how to end up with a trouble-free odor-free system, you're welcome to send me an email too. Meanwhile both of you can find some useful information if you the link in my signature.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein