Will head tanks gravity drain effectively?

[Bobby Lex]

Originally Posted by peghall

That's adding an unnecessary fitting whose only function would be to protect owner from failure to maintain the system, adding another layer to "whatever can go wrong, will."

I've never seen any need to add any additional equipment, especially any that require any maintenance, although I think I would run separate pumpout and dumpout lines, eliminating the tee.--Peggie

My Caliber 40 has its holding tank above the water line so it can be gravity-emptied at sea. Very simple. No pumps to fail. Open the discharge seacock. Wait a minute or two. Close it. Done! I really like how it works.

But....the hose leading from the bottom of the holding tank down to the discharge seacock is the first thing to fill with effluent when the head is used. And that stuff sits in the hose until the next time the tank is emptied at sea. (My guess is that even a dock-side pumpout doesn't get all the effluent that sits in that hose below the holding tank.)

The effluent just sits there, permeating the hose, 24/7.

To prevent that I installed a ball valve at the holding tank-to-discharge-hose fitting to keep effluent out of the discharge hose except when discharging overboard. That way I'm not having to replace that 3' section of discharge hose every 6 months or less because of permeation odors.

Bottom line: I do think there are circumstances when adding a strategically placed fitting at the holding tank outlet serves an important purpose, and doesn't overly complicate the system.

Bob

[NYSail]

Originally Posted by malbert73

I’m not sure I would want my head to pump into the bottom of holding tank. That could build up a lot of pressure if you fill it, against your joker valve.
20 gallons of sewage could make a mess if your joker valve fails.

He is not saying the inlet would be at the bottom of the tank…… he said the drain/discharge would be. Inlet is at the top

[SailingHarmonie]

Originally Posted by malbert73

I’m not sure I would want my head to pump into the bottom of holding tank. That could build up a lot of pressure if you fill it, against your joker valve.
20 gallons of sewage could make a mess if your joker valve fails.

I agree! I am a fan of gravity draining tanks, but the line from the toilet ALWAYS enter the top of the tank. Pumping into the bottom of the tank is just a dumb idea.

[peghall]

I’m not sure I would want my head to pump into the bottom of holding tank.


The idea that Kanter even suggested that makes as much sense as assuming he recommended putting the discharge anywhere but IN the bottom of the tank!



He just provided a list of parts that doesn't specify any locations for 'em! If you're not smart enough to know where to put them, this prob'ly shouldn't be a DIY project!


--Peggie

[team karst]

Imagine the excitement when a joker valve is pulled at 3 am no longer holding back 4’ of stuff.

[Jweyndling]

All Fountaine Pajot catamarans
Come with this kind of arrangement as standard Over many years I have never had the tanks fail to drain under gravity alone.

[gregfreed]

The system in my Passport 40 is very similar.
I’ve lived aboard her for 14 years. The key to happiness is; Only open the valve to drain the tank, then close it again.
You don’t need to wait till it’s absolutely full, however 1/2 or better will yield flawless results, even without a macerater.

[walt41]

A composting head with a solar vent is the best solution. No pumpout, holding tank pump or associated piping that clogs. There is no smell, urine legally goes overboard, and it will last several weeks before disposing mulch and solids in the garbage.

[Night_Sailor]

Originally Posted by peghall

That's dding an unnecessary fittinng whose only function would be to protect owner from failure to maintain the system, adding another layer to "whatever can go wrong,will."

A marine surveyor named Charles Kanter introduced the gravity drain holding tank about 30 years ago...he called it "The KISS (keep it simple stupid) MSD." He specified the parts needed:
1 tank
1 outlet seacock
1 inlet seacock (from the toilet)
1 "Tee" fitting (he used the same hose for both pumpout and overboard discharge)
hose clamps on minimum number of joints, double clamped
hose clamps for vent double clamped
Vent fitting
X Feet of hose or PVC pipe


I've never seen any need to add any additional equipment, especially any that require any maintenance, although I think I would run separate pumpout and dumpout lines, eliminating the tee.


--Peggie

I do it exactly as Peggy stated with separate pump-out, head-discharge inlet, and drain lines.

[walt41]

I would not rely on gravity to pass large solids through piping. Had composting head (Nature's Head) on my last two boats and am very satisfied.

[peghall]

Solids and quick-dissolve TP dissolve very quickly in water, plus they're broken up going through a manual toilet pump so unless you decide to open the drain in less than 15 minutes after a large solids deposit, that won't be a problem.



--Peggie

[malbert73]

And better yet, get a raritan elegance which will grind anything up and be super reliable.

[gs41escapade]

I'm no expert on head plumbing, but a few comments.

If you are at sea and underway, then when you open the head discharge, you will get some vacuum drag on the tank which will help. Most boats I've seen do not have a macerator for pump out from the tank, rather for pump up to the tank.

If you were to add one more valve before the T, then you could potentially shut that valve and use a wet/dry vac in blow mode to blow down from the pump out through the overboard to help clear it. Just a thought.

[walt41]

Sailed to Bermuda on a boat (Oyster 49) with gravity drain holding tank. It clogged during the trip and divers could not clear it. Had to search for a store with the right type of flexible hose to insert through the tank into the drain to ultimately drain it.