[C38] on and on head discharge

Thu Nov 3 14:18:28 EDT 2011

All,  This subject of vented loops is baffling and opinionated by experts.  My boat has been fully surveyed 4 times and never have they requested that the head overb'd loop have a vacuum breaker installed.  I've even heard of boats having a vacuum breaker installed on the engine exhaust overb'd, even though the exit is above the
WL.  I would recommend any body sealing their head overb'd.  In an emergency it could be very useful- ask Larry Malberg about his first Transpac and not being able to pump overb'd.  On how you use holding tank (15 gal, say 30 flushes max) come down on how you use your boat.  On an overnight race, six crew members, you have to ration what goes into the holding tank- solids into the tank, pee overb'd -even in inland waters, like Puget Sound.
With the head valving ( joker and flapper) working correctly,  my head bowl does not over flow, unless a human makes a mistake and leaves the pump intake open.
But as precaution, I always close the sea cocks for both the intake and overb'd, when leaving the boat.
Cheers, Steve O
Santa Susanna- #304 

> Date: Wed, 2 Nov 2011 09:14:51 -0700
> From: drstrong at ucdavis.edu
> To: listserve at catalina38.org
> Subject: Re: [C38] on and on head discharge
> 
> Dear Les and Steve:
> Both of you are people that I would take advice from. The story is 
> that nine years ago when I got the boat my insurer required the vented 
> loop. The boat has head to overboard discharge, direct, when the valve 
> is thrown to direct overboard. They didn't ask anything about the 
> plumbing, they simply required the vented loop from the head. The tank 
> has a vent, as Les describes, and were the overboard to exit from the 
> tank, that vent suffice for either tank or overboard. It would not 
> suffice for direct overboard that bypasses the tank, as mine can.
> I have never used the direct overboard discharge and have it pull 
> tied off as per USCG regs. Even when we sail down the Big Sur coast we 
> use the tank; why not?
> Nine years ago when I installed the vented loop, I knew much less 
> (I don't know nearly as much as many people on the blog even now). I 
> could have done it differently, I guess. I could have eliminated the 
> direct overboard completely. that would have required pulling the boat 
> and expensive glassing over the through hull hole. Or, I could have 
> re-routed the system: head to tank to over board, which would have 
> meant installing a pump from tank to overboard. Actually, since I don't 
> use the overboard, I could have forgotten the tank to overboard and the 
> pump. I could have asked my insurer what they would accept. At that 
> point, I wanted to be insured and the vented loop seemed easiest 
> (rerouting all discharge through the tank would have been easiest, since 
> I don't use the overboard, I wish that I could have read this post back 
> then). The vented loop hasn't caused any trouble that I can detect. The 
> grey water problem is solved by pumping a bit more to push the grey over 
> the top, but our head discharge usually isn't that grey, and a healthy 
> joker valve works perfectly.
> On the inlet side, the vented loop was easy. It is safe, and it was 
> recommended by two different boat wise guys that I talked to; they still 
> seem pretty wise; no problems from that install either. You can leave 
> the head in dry or wet position and sleep well.
> Don
> 
> On 11/2/11 8:24 AM, Steve Smolinske wrote:
> > http://www.boatus.com/boattech/casey/13.htm
> > http://www.thetford.com/HOME/PARTS/PermanentToilets/Headmate/tabid/575/D
> > efault.aspx
> >
> > Don Casey actually recommends that you do not put a vented loop on the
> > intake and that you do put one on the discharge. Attached excerpt from
> > Boat US has a page from his book. Our heads the Wilcox Crittenden
> > Headmate (now Thetford) has a duckbill ball (joker), then there is a
> > flapper valve in the toilet base. Link to the manual is attached the
> > duckbill is #23 and the flapper is #32 in the blown up schematic.
> >
> > On the inlet side there is another flapper valve that is engaged with
> > the flush or dry flush option via the small lever by the pump handle.
> > This should never be left in the dry position, I know many people leave
> > it in that position when finished with the head in order to leave the
> > inlet line through hull open, and yes while in that position it does
> > stop the water from entering the bowl, however the flapper valve is a
> > rubber gasket with a small disc riveted to the flapper, This seal will
> > and does take a compression set and the metal disc will deform if left
> > in that position. I know because I just replaced it because my head
> > would no longer work, I talked to Thetford who told me do not leave
> > your boat head in the dry flush position.
> >
> > Steve
> >
> >
> >
> > -----Original Message-----
> > From: listserve-bounces at catalina38.org
> > [mailto:listserve-bounces at catalina38.org] On Behalf Of les
> > Sent: Tuesday, November 01, 2011 10:54 PM
> > To: listserve at catalina38.org
> > Subject: Re: [C38] Vented loop for head discharge
> >
> > You would never put a vented loop in the head discharge. Or perhaps I
> > should say I never would. The holding tank is vented out the port
> > stanchion near the forward lower shroud.
> >
> > An anti-siphon valve with a loop is often inserted between the hand or
> > mechanical pump and the bowl flush inlet, to prevent the siphon effect,
> > and that loop never has anything but raw water (salt or fresh depending
> > on where your boat is sitting).
> >
> > If you think about the direction of flow, from the inlet thruhull
> > through the pump to the bowl, you will realize that the pump valves will
> > NOT prevent siphon effect, because that is the direction they are
> > designed to pass water to flush the bowl. This is especially true if
> > the valve on the pump is left in or falls to the flush position.
> > The flush inlet and output valves are in the pump body and I believe are
> > generally popet type valves.
> >
> > The duckbill valve is typically in the head discharge. Someone can
> > correct me if I am wrong about all this. I never rebuilt my pump, but
> > did have the head replaced once.
> >
> > Generally flow is as follows:
> >
> > Head inlet thru-hull
> > hose to pump flush side inlet
> > pump
> > hose from pump to bowl rim flush inlet
> > toilet bowl
> > toilet base
> > duckbill valve to head flush pump
> > pump flush side
> > duckbill valve to pump outlet
> > hose to y valve
> > A side of y valve to overboard
> > B side of y valve to holding tank
> > holding tank
> > vent hose to port stanchion vent
> > outlet to pumpout valve
> > hose from pumpout valve to pumpout fitting on deck port side
> > forward.
> > At the other side of the TEE from the pumpout valve is the
> > macerator
> > Hose from macerator output to overboard thru hull port side
> > under galley settee.
> > thruhull to raw water (ocean, lake or whatever). 
> >
> > To pump out, open the pumpout valve, and connect the pumpout
> > hose to the pumpout fitting (wear a mask. I once had one do something
> > very untoward, and it was horrible on my skin!!!)
> > Once pumpout is finished, close the pumpout valve (you do not
> > want the macerator to back up to the pumpout side.
> >
> > Regards,
> > Les H
> >
> > On Mon, 2011-10-31 at 23:43 -0700, Steve Smolinske wrote:
> >> Question for anyone with a vented loop in their head discharge.
> >> Looking at it on paper it seems that the pressure of the grey water in
> >> the section from the head to the vented loop would be enough to leak
> >> back into the toilet bowl. I know there is a duckbill valve and a
> >> flapper valve in the head to stop the reverse flow, but as we all know
> >> if you leave the discharge seacock open the head will fill up. Does
> >> the vented loop work because the head pressure of the grey water in
> >> the run from head to loop is not as great as that coming from the
> >> seacock? Any experiences are greatly appreciated. Thanks
> >>
> >> Steve
> >> _______________________________________________
> >> Listserve mailing list
> >> Listserve at catalina38.org
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> >
> >
> >
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> 
> -- 
> Donald R. Strong
> Professor
> Dept. of Evolution and Ecology
> University of California, Davis 95616
> 
> 
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