Sanitation redesign

[Steven UK]

so i just purchased a boat that was built without a holding tank and this is what i came up with as a replacement, design constraints are space and cost.

the boat comes with a defunct vacuflush pump that i am hoping to re-purpose as a overboard pump...

go for it...

Best regards Steven

hopefully there is an image attached...

[Steven UK]

try again...

[Bill O]

Steven,
Mostly your design looks fine, but may want to increase your vent size to 1" or larger.

Don't think you need 2 direct overboards as how you have it currently designed. Probably will need a Y from the head to have one direct over then the other go to the tank. From the tank out you'll want another Y to go to a deck fitting for a pump out facility and the other to pump overboard.

The overboard discharges can only be used offshore and not in the Great Lakes, etc., so you'll want the deck fitting for pump outs.

Also search the CF threads and look at the "hoses" used between the head and tank. Eventually the standard marine hoses will eventually permeate, but since you are making it new, use as much sched. 40 PVC as possible to save yourself from the stench in a few years. May need to use some hose but keep it to a minimum.
When you get to salt water, you'll want to flush with fresh water, not salt water. The critters found in sea water will die in your tank and eventually smell worse then the stuff you are contributing to the tank.


Bill O.

[Mike OReilly]

If you have the space, you could install a composting head and be done with it.

[Cheechako]

-Not sure you need an air vent in the exit hose...? It's going to close with crap immediately any way and your tank is above waterline.
-If you could get the tank so the bottom is at or above waterline you could have a bottom drain and no pump. The one boat I was able to do that on worked really well draining by gravity and water flow past the fitting.
-I've noted before that the intake vent valve is best in the hose that goes from the toilet pump to the bowl, rather than from the seacock to the pump.. Although it's often not too convenient to put it there. I did find on my boats that had the vent where you show it, that they would gurgle air while pumping the lever and not pump water as well.

[peghall]

I would put TWO discharge fittings in the tank--one for a line going directly to the deck pumpout fitting, the other for a line going directly to an overboard discharge pump and thru-hull....eliminating a y-valve. If you want the ability flush the toilet directly overboard, you will need a y-valve in the toilet discharge line.

1" vent line as short, straight, and close to horizontal as possible.

If the VacuFlush pump (S-Pump) still works, repurposing it to dump the tank is a good idea.

You haven't said what the make/model of your toilet is...if a manual toilet, the inlet vented loop needs to be installed between the pump and the bowl (see drawing in the owners manual for your toilet) at least 6-8" aboe the bowl AT MAX HEEL...which on most sailboats puts it 2-3 feet above the bowl. If you have an electric toilet, it may or may not have a choice of where to put it. If it has to be installed between the thru-hull and the pump, you'll need an electric solenoid valve that's wired to the flush button.

You're welcome to give me a shout via PM or email if you need to discuss in more detail than is practical in open forum.

--Peggie

[Steven UK]

Peggie
the vented loop is after the inlet pump i used the hydraulic symbol for the built in 'Loo" inlet pump. i did include a 'Y' valve after the toilet that will either go to tank or to a 'Y' fitting just before the vented loop.

one of the things that concerned me the most was the vented loop and the 'Y' fitting location. it was my understanding that the vented fitting needed to go just before the through hull above the heeled water line. but i do see the 'Y' fittings drawn just before the through hull.

Bill
i can go to a 1" vented line if needed.

Cheechako
i could make the whole thing above the water line but i would be halving the capacity from the currently small 7 gallon. i can fit about a 1' cube tank and half of it would be below the water line.

also i was thinking there was some benefit to having all the tank openings on the top, i don't like the idea of slow leaks on this particular boat system...

[Bill O]

Originally Posted by peghall

I would put TWO discharge fittings in the tank--one for a line going directly to the deck pumpout fitting, the other for a line going directly to an overboard discharge pump and thru-hull....eliminating a y-valve. If you want the ability flush the toilet directly overboard, you will need a y-valve in the toilet discharge line.

1" vent line as short, straight, and close to horizontal as possible.
--Peggie

I agree w/Peggie's suggestions and it would be nice/ideal to have 2 separate discharge fittings on the tank and eliminate a y valve. Practically speaking, I've never seen a holding tank w/2 discharge fittings (unless custom). If you are re-using your old tank, it may be difficult to add another discharge tube/fitting, especially if it's a plastic tank. If a metal tank, it may be easier to add one if you have a welder on hand to help make the tube/flange/fitting.



Bill O.

[peghall]

If you are re-using your old tank, it may be difficult to add another discharge tube/fitting, especially if it's a plastic tank.

Actually very easy, thanks to a li'l gizmo called the UniSeal UNISEAL. It's used quite a bit to add and relocate fittings in plastic and FG tanks. A short piece of PVC pipe becomes the new hose fitting.

Steven...There's definitely a benefit to having all the fittings on the top of the tank...however that requires at least 5" clearance above the top of the tank. If a 7 gal tank is all you can fit into the location you've chosen, we need to find another location for the tank! 'Cuz that won't be possible, and even if it were, 7 gal is barely enough to last 2 people 24 hrs.

--Peggie

[Bill O]

Well I guess you can learn something new everyday on CF.

Thank you Peggie for showing us that you can add another port to a plastic tank w/o doing plastic welding to re-enforce the area. Didn't know those fittings existed. You truly do know your sh../stuff!!! lol

Bill O.

[Cheechako]

Originally Posted by peghall

I would put TWO discharge fittings in the tank--one for a line going directly to the deck pumpout fitting, the other for a line going directly to an overboard discharge pump and thru-hull....eliminating a y-valve. If you want the ability flush the toilet directly overboard, you will need a y-valve in the toilet discharge line.

1" vent line as short, straight, and close to horizontal as possible.

If the VacuFlush pump (S-Pump) still works, repurposing it to dump the tank is a good idea.

You haven't said what the make/model of your toilet is...if a manual toilet, the inlet vented loop needs to be installed between the pump and the bowl (see drawing in the owners manual for your toilet) at least 6-8" aboe the bowl AT MAX HEEL...which on most sailboats puts it 2-3 feet above the bowl. If you have an electric toilet, it may or may not have a choice of where to put it. If it has to be installed between the thru-hull and the pump, you'll need an electric solenoid valve that's wired to the flush button.

You're welcome to give me a shout via PM or email if you need to discuss in more detail than is practical in open forum.

--Peggie

Hey Peggie, did you mean Vertical? or ....why have a vent line Horizontal?

[Steven UK]

Right now the drawing doesn’t show a deck pump out just a vent and vented loop. The current setup on the boat is a five gallon diesel Gerry can, so whatever I do will be an improvement. I’m more worried about the ‘Y’ fitting... just before the vented loop or just before the through hull. I have very limited space available as the boat didn’t come with any holding tank when new. For the sake of guests I would rather stick with a traditional system but this would be an ideal candidate for a composter....

Regards Steven

[Steven UK]

P.s. I’ll be on the boat for a year traveling round. Hopefully more sailing less marina time...

[Cheechako]

Originally Posted by Steven UK

Cheechako
i could make the whole thing above the water line but i would be halving the capacity from the currently small 7 gallon. i can fit about a 1' cube tank and half of it would be below the water line.

also i was thinking there was some benefit to having all the tank openings on the top, i don't like the idea of slow leaks on this particular boat system...

Yeah, I made a tall thin one bulkhead mounted in a mechanical closet due to limited room. But the height helped give head for the gravity flow out. It made the hose runs nice and short that way too! The head pumped into the top (not shown)

[peghall]

Originally Posted by Cheechako

Hey Peggie, did you mean Vertical? or ....why have a vent line Horizontal?

Because the gasses generated by organic matter--even odorless CO2 generated aerobically--are heavier than air...they don't rise in a vertical vent line and ambient air out side doesn't "fall" down one. A 45 degree rise is about as much of a vertical rise that'll allow air exchange to happen.



--Peggie