Advice on marine toilet system

[JPonHudson]

Ahoy Mates,
I need some advice on my system. I currently have a holding tank behind and above the toilet (green) which I think might be odd since all the boats I have looked at had a tank either on the same level or below the toilet. I am wondering how a manual toilet pump was able to pump the waste this high.
The waste pump out is right above the head a so is the vent. There is a blocked thru hull drain under the sink (red) and another under the lazarette to the left (red) Water intake (blue) (operational) is right above that thru hull.
I want to be able to make a system that allows me to use either fresh water from the tank or sea water, and option to either keep the waste in the tank or discharge out while off shore (where legal). I guess that means two Y valves one for water and one for waste.
My wonderings are...
How was the manual toilet able to pump the waste so high up. It does not seem possible?
I have heard that many boats like mine (1978 S2 9.2a) use the area with the water intake to store the holding tank but this is where the transducer is placed and it looks like the bottom of the tank would be below the thru hull which I think does not sound correct.
Please share any thoughts or suggestions. I am not new to sailing but new to designing marine toilet systems. I am trying to decide to either go (no pun intended) with manual or splurge for electric model. My concern is that manual toilets appear to be unreliable and too complicated for visitors to use.

[GordMay]

Originally Posted by JPonHudson

...
I want to be able to make a system that allows me to use either fresh water from the tank or sea water, and option to either keep the waste in the tank or discharge out while off shore (where legal). I guess that means two Y valves one for water and one for waste...

You don’t need/want a “Y-Valve” for selecting fresh or salt water, to flush your toilet.

Indirect Connection: Any connection, between potable water piping, and sewer-connected waste, shall be protected by an air gap, to prevent contamination of potable water, by the backflow of sewage.
You can use a hand held shower head, with flexible hose, to flush your toilet, with fresh water. Keep the shower head at least 1-1/2" above the rim of the toilet.

[pjShap]

Having the holding tank above the water line allows you to drain it overboard, where permitted, by simply opening a drain valve. Very useful if you sail coastal and are frequently over 3 miles from shore.

[Mike OReilly]

Have you considered going compost? Waaay easier, safer, simpler, and IMO, better over all -- IF you're talking small crews (2 to 3 people).

[EmeraldCoastSailor]

One of the best upgrades I ever did on the Beneteau I sold a few months ago was replacing the stock bowl manual pump toilet with a standard size electric toilet. The holding talk is mounted above the toilet; the manual pump and then the electric pump pushed the waste uphill no problem.

When I wanted to use freshwater I would simply use the faucet at the sink to fill the toilet bowl.

[Fore and Aft]

Our bathroom sink outlet seacock was also our toilet seawater inlet. When we wanted a fresh water flush we would turn the seacock of and fill the sink. Then flush the toilet until the sink was empty.
Cheers

[SailingHarmonie]

Originally Posted by JPonHudson

Ahoy Mates,
I need some advice on my system. I currently have a holding tank behind and above the toilet (green) which I think might be odd since all the boats I have looked at had a tank either on the same level or below the toilet. I am wondering how a manual toilet pump was able to pump the waste this high.
The waste pump out is right above the head a so is the vent. There is a blocked thru hull drain under the sink (red) and another under the lazarette to the left (red) Water intake (blue) (operational) is right above that thru hull.
I want to be able to make a system that allows me to use either fresh water from the tank or sea water, and option to either keep the waste in the tank or discharge out while off shore (where legal). I guess that means two Y valves one for water and one for waste.
My wonderings are...
How was the manual toilet able to pump the waste so high up. It does not seem possible?
I have heard that many boats like mine (1978 S2 9.2a) use the area with the water intake to store the holding tank but this is where the transducer is placed and it looks like the bottom of the tank would be below the thru hull which I think does not sound correct.
Please share any thoughts or suggestions. I am not new to sailing but new to designing marine toilet systems. I am trying to decide to either go (no pun intended) with manual or splurge for electric model. My concern is that manual toilets appear to be unreliable and too complicated for visitors to use.

The design you describe of a holding tank set above the water level is 100% normal and not at all a problem for a manual toilet. Many boats use this design, and it has many advantages. Our boat has used this system for 30 years.

Be very careful with piping fresh water directly to the toilet. The possibility of reverse flow needs to be impossible, for obvious reasons. The simplest solution might be the best. We flush our toilet with fresh water using the handheld shower. Easy, simple, foolproof.

[CaptTom]

I actually prefer manual flush. To me, they're much simpler, and it's easy enough to keep a set of spare parts. They're also quieter, and avoid the problem of people thinking they can put anything they want in the head, close their eyes, push a button and it disappears. Having to pump it yourself makes you a bit more invested in the outcome.

You should have no trouble flushing "up" with manual or electric.

Avoid Y valves. As mentioned, if you want fresh water flush that would have to be on an isolated input. I doubt you'll want to switch back and forth anyway. If you're going to be away from the boat for a while, you can do a quick rinse with a bucket or the shower nozzle if it's handy.

For discharge, you can "T" the deck pump-out hose with the macerator or direct discharge plumbing. Again, no need for a Y valve. With the tank above the waterline, a direct discharge down from the tank is possible, just be aware that solids may clog it, where a macerator would, well, macerate it and better clear out any solids.

[peghall]

There's a much better way that also rinses the sea water out of the entire system (water added to the bowl only goes out the discharge line):


Assuming that, like most sailboats, your sink drain thru-hull is below waterline...Disconnect the toilet intake hose from the thru-hull (close the seacock first!) and r-route it to tee or wye it into the sink drain line as close to the seacock as possible because the connection must be below waterline to work. You'll be left with an unused thru-hull that you can repurpose to use for a washdown pump and probably be able to shorten the intake line.

This will allow you to flush normally with sea water. To flush with fresh water, close the drain seacock, fill the sink with clean fresh water and flush the toilet. Because the seacock is closed, the toilet will draw the water out of the sink, not only providing a fresh water flush, but also rinsing the sea water out of the entire system—intake line, pump, channel in the rim of the bowl and the discharge line,(Water poured into the bowl only rinses out the toilet discharge line), eliminating odor from sea water left to sit and stagnate in the system. If your toilet is electric, be careful not to let it run dry…doing so can burn out the intake impeller. Or you can keep the sink drain seacock closed except when it's needed to drain the sink and flush with fresh water down the sink all the time...your choice.
It may also be necessary to keep the sink plugged except when in use, with a rubber sink plug. Otherwise the toilet may pull air through the sink when you try to flush, preventing the pump from priming.


--Peggie.

[b.needalman]

Modern boats have the holding tank over the water line. The tank empties by gravity rather than needing a macerator pump. Feature, not a bug.

[nmccubbin]

On Milvina, our head pumps manually to an above-waterline holding tank. It can either drain to ocean or be pumped out from deck
At sea, we just leave the drain valve open.
Very simple and has worked well for 20 years
No Y, or Tee valves
I have never owned a Y valve, but have had to fix a few. I have yet to see one that is well made
I second the advice to avoid a fresh water connection. We do occasionally flush with fresh water from the shower, primarily when on the hard and planning to launch before the tank is full

[mikk60]

I have the drain from the sink connected to the head for fresh water flush

[FlyingScot]

Raritan makes a SeaFresh model that switches between sea and fresh water with a simple flip of a switch. We have one now and so far it's been great.
Like the ever helpful Peggie says, it doesn't solve the water from the through hull to the bowl, just downstream.

[mikk60]

All my sink water goes thru head. Head never sees saltwater

[Dockhead]

Originally Posted by pjShap

Having the holding tank above the water line allows you to drain it overboard, where permitted, by simply opening a drain valve. Very useful if you sail coastal and are frequently over 3 miles from shore.

That's fine, but is it really worth it just to eliminate the macerator pump? The macerator pump not only pumps overboard from a below waterline tank, but also processes the waste so it breaks down much faster. You can also use a manual pump if you are a fanatic about simplifying the electrical system.



There are a number of disadvantages to having the tank above the level of the toilet. One is reduced efficiency of the toilet. I prefer my black water times as low as possible.