[C38] on and on head discharge
Don Strong
drstrong at ucdavis.edu
Wed Nov 2 12:14:51 EDT 2011
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
>> _______________________________________________
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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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