Combining discharges

[Byrnerc]

I hate putting holes in the hull. Does anyone know of a problem with using one thru hull for two waste discharges? I want to install a macerator pump to the holding tank. Instead of adding another thru-hull valve, I could plumb it to the galley sink thru-hull using a diverter valve. The diverter would make it impossible to accidentally pump into the sink, the thru hull being below water would prohibit smells from wafting up as long as I ran fresh water to flush below the diverter. I haven't found any other threads discussing this so where will I go wrong?
Rossco

[thinwater]

For sure, I would mount the switch next to the diverter valve, with a sign!


Actually, I would just add a thru hull.

[JoeRobertJr]

Hi, Rossco,
I am with you on limiting the number of through-hulls.
I assume you mean that you want to add the macerating pump "from" the holding tank, not "to" the holding tank.
Potential problems?
1. Energizing the pump while the diverter valve is in the wrong position. Thinwater's suggestion for signage and switch location would help mitigate that.
2. I expect the diverter valve would need the same tie-wrap seal in the closed position as other waste discharge valves while operating in US waters.

Beyond that, I don't see any problems with your plans.

[s/v Jedi]

We use 2” diameter standpipes for discharge. Ours are schedule 80 PVC but I would use fiberglass pipe from Centek if doing it today. You laminate it into the hull, with additional support inside of the hull. The pipe goes up to just above waterline, where a piece of exhaust hose connects to a PVC manifold for the discharge hoses.

Of course this requires having enough height for it.

[peghall]

Toilet flush water intake line is the only sanitation system plumbing that can be teed into a sink drain line because USCG regs forbid combining gray water ("galley, bath and shower water") and black water (Sewage) plumbing due to the risk of sewage migrating into a sink, exposing people to e-coli bacteria.
So Unless you already have a thru-hull that allows the toilet to be directly discharged overboard, you're gonna need a new thru-hull for the macerator pump.


--Peggie

[thinwater]

Originally Posted by peghall

Toilet flush water intake line is the only sanitation system plumbing that can be teed into a sink drain line because USCG regs forbid combining gray water ("galley, bath and shower water") and black water (Sewage) plumbing due to the risk of sewage migrating into a sink, exposing people to e-coli bacteria.
So Unless you already have a thru-hull that allows the toilet to be directly discharged overboard, you're gonna need a new thru-hull for the macerator pump.


--Peggie

There you go.


Household plumbing shares drains, but ...

• They are gravity drains (no pumps).
• The main drain is much larger, either 3" or 4".
• They always have P-traps.
• And sometimes it does go wrong.

[Byrnerc]

Thank you all and especially Peggie for saving me from getting into big do-do with the CG. Pun intended. I guess that means it's another hole.
Love your book, Peggie. I'm still trying to figure out how to get more ventilation into the holding tank..

[peghall]

I'll be glad to help you sort out how to do that on YOUR boat...Send me a PM after life recovers from the holidays.


--Peggie

[RaymondR]

Went the single overboard route for all discharges on my steel boat and fairly quickly decided that it was a poor arrangement and welded in a steel standpipe to height above the waterline. Just the constant concern for what may eventuate overcame my desire for minimum penetrations.

[Byrnerc]

Thanks Peggie, will do. Later...

Raymond, sometimes I get too hung up on a peeve and "can't see the forest for the trees". That's why it's good to use this forum. Thanks.