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Scubado 03-23-2004 07:57 AM

Holding Tank
Hi All,
I''m getting ready to install a Wilcox Crittenden Head mate in my P-26. Do I need to be SURE the holding tank inlet from the head is level with or lower than the discharge from the head. Is gravity a factor here ? If the tank is a bit higher would a vented loop solve any possible problem?
Any advice, info, etc. is greatly appreciated.
Thanks, Chet

capttb 03-23-2004 02:18 PM

Holding Tank
I think the gravity part is critical and a loop would make problem worse,if loop is higher than head you couldn''t flush, it would just overflow. If head is lower you will always have "product" trying to get to the head (gravity, you can''t fight it). Line from head leads to top of tank or the bowl would fill to level of tank.

GordMay 03-24-2004 01:24 AM

Holding Tank
There is no reason to plumb the W.C. (Head) discharge “down” into the holding tank. It’s not a gravity system, as the W.C. waste discharge is pumped to the tank (or overboard).
The Head discharge is plumbed, through a Vented Loop, to the top of the Holding Tank. The head is normally lower than the holding tank.

“cpttb’s” advice that “gravity is critical”, and “a loop would make problem worse” is incomprehensible, to me :). He’s right that the “line from head leads to top of tank”.

See the basics at “Installing a Head” - by Don Casey


Scubado 03-24-2004 05:34 AM

Holding Tank
I want to thank you guys for replying to this message. I''m going to check out the site as suggested. Marine plumbing is not my strong point.
Thanks Guys

Scubado 03-24-2004 05:51 AM

Holding Tank
Hey Gord,
I get a bit confused about htis "vented Loop" deal. do I need that or not. My head would move below the waterline when heeled over, but who''s using the head then anyway.
Is there a line of any type (hose) coming of the top of the vented loop? Pictures don''t show any but description mentions something about it. The boatus site description.
Again, I''m at your mercy for info.
Thanks, sorry to be so dumb about this but I really don''t want an accident on my hands if this is put in wrong. YEEECH

capttb 03-24-2004 06:22 AM

Holding Tank
I''m not familiar with that particular head (must have some kind of ''trash pump''?) but most are gravity feed. According to CG & Yachts standards, all below waterline thru hulls ending below WL (at tank) should have vented loop which is above WL at all angles of heel. This is to prevent flooding the boat and/or filling the tank should seacock fail or be left open. Manual for Jabsco Macerator pump states vented loop required for below waterline thru hulls also. Mostly affects line from macerator pump & water intake line for head. I know Catalina didn''t put loops in either place in my boat and it may be physically impossible to retrofit without extensive mods. They did put labels all over advising to only open thru hulls when in use which is what I do.
Just looked at that page posted above & looks good but a little confusing, maybe I''m just being dense today but the tanks higher than head is throwing me, flushing uphill?

williamjchampion 03-24-2004 08:30 AM

Holding Tank
Lots of different ways you can plumb this. Assuming you flush with sea water and your head is below the waterline (almost inevitable), you need a vented loop in the water supply line to keep siphoning from sinking the boat. The (normally 1 1/2 inch) discharge line may or may not need a vented loop. If you are just going into the holding tank - no. If you have a Y-Valve or similar arrangement that allows you to pump overboard to a thru-hull - you''ll want a vented loop in that line as well. Some vented loops can be fitted with a small tube that attaches to the vent and, from there to thruhull (above waterline) vent (similar to a gas tank vent). Others do not. The holding tank, however, needs to be vented, preferably w/ 3/4 inch tubing. Get good quality odorproof hoses. Look at Casey''s book. Also, I believe the West Marine catalog has a couple of simple diagrams that may be helpful.

WHOOSH 03-24-2004 08:45 PM

Holding Tank
Just one addition to William''s thorough reply: the intake line''s antisiphon vent needs to be between the head (toilet) pump and the bowl connection point. If you hook it up where you may think it goes - somewhere between the intake thru-hull and the head (toilet) pump, it won''t work.

The Forespar a-s vents seem to last indefinitely and I like the fact you can ask them for a replacement duck-bill or two (the little one-way rubber valve that gives the fitting its anti-siphon capability) which they usually will provide you for free.


Scubado 03-25-2004 09:48 AM

Holding Tank
OH Man,
Here I thought this would be a simple matter. The toilet I''m planning to use is a manual head. There will be NO overboard discharge of waste due to Lake restrictions. I''m told this head pumps the waste manually, that is a pump handle, to the holding tank. My impression of the vented loop theory is primarly for systems that have a through-Hull overboard discharge for waste when in outside the 3 mile limit.
If I''m reading all this great info right, It would be a preferred situation if the tank inlet from toilet is lower than toilet discharge. RIGHT !! Ok Guys, thanks,

capttb 03-25-2004 04:04 PM

Holding Tank
On system you describe you are correct that only vented loop you should have (many boats don’t) is on inlet for toilet (to flush head) I think. If I understand correctly your system will have 4 lines or hoses:
•¾” inlet from thru hull to head (flushing water)
•1.5” From head to Top of holding tank (toilet discharge)
•1.5” From Bottom of tank to deck fitting (pump out)
•¾” From top of tank to vent
But I’m back to thinking tank (& thus inlet) must be lower (or level) then head in this system again.

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