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Go Back   SailNet Community > On Board > Gear & Maintenance > Holding Tank
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Topic Review (Newest First)
04-01-2004 12:24 PM
Scubado
Holding Tank

Well Gentlemen,
I think we beat this one up pretty good. With all the various theories, specifications, links and experience donated to this question, I think I can get the job done. I thank you all.
Chet
03-28-2004 08:55 AM
capttb
Holding Tank

Just looked at Jabsco site Gord posted, 9'' head rating for discharge pump (~4.5 PSI) I''ll be darned, never even occurred to me that tank could be higher I just imagined the tank always trying to empty itself into the lower toliet. Heads are such a pain.
03-27-2004 06:05 AM
GordMay
Holding Tank

Vented Loops on Below Waterline Heads:
If the Head is installed below the waterline, or may be below the waterline at any angle of heel (virtually always on a sailboat) - properly positioned Vented Loops must be installed.
Vented Loops should be installed on BOTH the Raw-Water Intake Line, between the Intake Seacock and the Head - AND - also on the Head Discharge Line between the Head and the Holding Tank.
ADDITIONALY, a Vented Loop should be installed in the 3/4" Hose between the Toilet Pump and the back of the Bowl. The factory-installed 3/4" Hose must be removed, and a new (longer) Hose c/w Vent installed.
The top of all the Vented Loops must be (about 8") above the waterline at the greatest angle of heel.
See:
http://www.raritaneng.com/pdf_files/compact_II/L219compactIIv0502.pdf
and
http://jabsco.com/prodinfo/overview/43000-0686_ds.pdf

Of course, sub-standard installations abound - and most of them work just fine - and havn''t sunk their owner''s boats. So maybe these Loopless schemes are "good enough".
Or you could do it right.

OMHO
Gord
03-26-2004 04:17 AM
williamjchampion
Holding Tank

With no overboard discharge, you will not need a vented loop in the waste line. Capttb''s response is right, except I agree with alanporter that you won''t need to locate the tank inlet below the toilet outlet (virtually impossible on most sailboats that I know).

If you are using lake water to flush (i.e., a thruhull), you still would be prudent to include a vented loop in the intake line. There are a lot of boats that fail to do this, but if the pump seals were to fail, you could siphon the lake into your boat. WHOOSH is right about the placement of the antisiphon vented loop, but that is frequently tricky with a head like the W-C you have. The toilet will still work with the vented loop between the thruhull and the toilet pump, but you will have to give it quite a few pumps to establish a prime and you''ll hear a nice squeal as the air escapes from the duckbill flap in the vented loop.
03-25-2004 05:36 PM
alanporter
Holding Tank

Hello Scubado. You appear to have got some confusing answers. On the lake, with no overboard discharge, you do not need an anti-syphon vent. The toilet outlet can be below the tank inlet, mine is 18 inches below, and has been for the past 28 years with no trouble at all. The toilet hand pump can push the effluent upwards of three feet above the toilet outlet, provided the piston seal does not leak.
Good luck
Alan
03-25-2004 05:04 PM
capttb
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.
03-25-2004 10:48 AM
Scubado
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,
Chet
03-24-2004 09:45 PM
WHOOSH
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.

Jack
03-24-2004 09:30 AM
williamjchampion
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.
03-24-2004 07:22 AM
capttb
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?
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