Heads outlet hose vs waterline

[cmedsailor]

Does the heads outlet hose need to be directed above waterline before going to the Y-valve that is before the WC “out” seacock or holding tank (holding tank is below waterline)? I have noticed than in my boat the outlet hose makes a large loop before going to the Y-valve even though there is no restriction on space and could simply go directly. The result is a lot of hose filled with black water in it. And despite the number of pumps I never hear it empty of water. And I think this is the reason why my joker valve fails often.
Your comments please.

 

[Graham376]

On both our heads, the outlet and inlet pipes loop up 2ft or more above waterline and we don't have anti-siphon valves.

 

[prv]

Some part of the system needs to go well above the waterline between the seacock and the toilet. Otherwise, you have a hole in your hull leading to the inside blocked only by some very cheap rubber toilet parts. However, it doesn’t matter exactly where this loop is.

Pete

 

[lw395]

Without anti-syphon valves, the raised loops are not going to work unless they are emptied of water. That's what a syphon is. A raised loop full of water.
Fit a holding tank.

 

[RichardS]

Without anti-syphon valves, the raised loops are not going to work unless they are emptied of water. That's what a syphon is. A raised loop full of water.
Fit a holding tank.

Although presumably the ultimate determinant is whether the final heads outlet is above or below the waterline? My outlet is a few mm below the waterline so that as the waves move the boat, the top of the outlet just lifts above sea. Presumably this is, in part, designed to ensure that a syphon is extremely unlikely, although, with my holding tank above the waterline, a syphon is impossible anyway.

Richard

 

[Hacker]

Always remember that the outlet needs to be aft and above the inlet!

 

[RupertW]

Although presumably the ultimate determinant is whether the final heads outlet is above or below the waterline? My outlet is a few mm below the waterline so that as the waves move the boat, the top of the outlet just lifts above sea. Presumably this is, in part, designed to ensure that a syphon is extremely unlikely, although, with my holding tank above the waterline, a syphon is impossible anyway.

Richard

Great in a catamaran but as I’ve learnt if you are on long sail on one tack in a monohull then siphons can overwhelm an electric bilge pump very easily. Not anything to do with our lavatory system as our outlet goes into the top of a high holding tank but if your side deck gets awash in gusts and big waves then every outlet is below the waterline on that side sometimes.