[C38] vented loop & head discharge

Don Strong drstrong at ucdavis.edu
Mon Nov 7 09:11:05 EST 2011 

C38ers.
BoatUS  has a link on their site about the vented loop for head discharge.

http://www.boatus.com/boattech/casey/13.htm

The system on Discreet Charm is identical to the third image down, which 
I used as a guide to installing my vented loops on intake and outflow 
from the head.
Regards, Don

On 11/3/11 11:56 AM, Steve Smolinske wrote:
>
> For  some reason I did not get Don's email for 11/2 in my box, had it 
> not been for Steve O forwarding it in his post I would not have seen 
> it.  Not sure what the problem is, btw Chuck my IT guy is  looking at 
> my system at home today to try to  resolve the attachment issue.
>
> As for the head discharge, sounds like a good topic for a future 
> article, I will do some research and find out  if there is an ABYC 
> requirement or recommendation for a vented loop in the discharge.   I 
> know I have seen a few articles about boats sinking because  of failed 
> heads, but  that really could be traced back to a root cause  of  an 
> open through hull.   On the intake side and I am guilty of leaving my 
> through hulls open from time to time what  I did was installed a valve 
> mounted on the bulkhead under the drawer next to the head, so when 
> using the head while sailing you operate the flow of water on/off 
> right there at the side of the head rather than crawling around to 
> open up a through hull.  On the back side the hose to the through hull 
> is double clamped at both ends as should all below the waterline 
> fittings be secured.
>
> Attached diagram is what I am planning on doing with the discharge 
> side of the head.  I need to close  the current macerator through hull 
> in order to make room for additional water tankage under the port 
> settee, this led me to plumbing the macerator into  the head discharge 
> line, then it grew to  I might as well close the grey water through 
> hull under the sink as  well by installing a sump tank in the bilge 
> for the head sink, and shower sump.  I have included vented  loops 
> where in theory water backing up  could  spill over  and enter the 
> boat  and sink her.   The only thing I think could be improved would 
> be to replace the macerator with a hand pump so that there is no issue 
> with a burnt out pump while at sea, should the pump in the bilge sump 
> tank fail that could always be emptied by hand and a small bailing cup.
>
> Steve
>
> *From:*listserve-bounces at catalina38.org 
> [mailto:listserve-bounces at catalina38.org] *On Behalf Of *S Orton
> *Sent:* Thursday, November 03, 2011 11:18 AM
> *To:* Cat 38
> *Subject:* Re: [C38] on and on head discharge
>
> 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 <mailto:drstrong at ucdavis.edu>
> > To: listserve at catalina38.org <mailto: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>
> > > [mailto:listserve-bounces at catalina38.org] 
> <mailto:[mailto:listserve-bounces at catalina38.org]> On Behalf Of les
> > > Sent: Tuesday, November 01, 2011 10:54 PM
> > > To: listserve at catalina38.org <mailto: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
> > >> _______________________________________________
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> > >> http://catalina38.org/mailman/listinfo/listserve_catalina38.org
> > >
> > >
> > >
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> > --
> > Donald R. Strong
> > Professor
> > Dept. of Evolution and Ecology
> > University of California, Davis 95616
> >
> >
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-- 
Donald R. Strong
Professor
Dept. of Evolution and Ecology
University of California, Davis 95616

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