Background: When we hauled Tehani (1999 Mk II) in the fall, there was a dribble of "water" coming out of the sanitation overboard. The boatyard supervisor was quite upset, and we had to quick put a plug in to keep the stuff inside the boat. For the winter, I just took the plug out and rinsed everything out.
Looking at the system this weekend, the only way liquid can get to that overboard is from the output of the macerator pump, or back flow from the deck pump-out. Thinking that the most likely cause is a failure of the seacock valve, allowing flow from the holding tank through the macerator pump, I unbolted the valve body off the seacock to inspect. I found that one side of the handle housing is broken off, which allows the handle to rotate a little beyond 90 degrees from "FLOW". This actually jacks the valve internals out and would allow a little flow.
So, I need to replace the valve, which is now on order from Catalina Direct.
What surprised me is that there was no vented loop between the macerator pump and the overboard discharge. Thinking about this further, there was a time, late in the season, that we discovered the WC overflowing with seawater, which would have come from the overboard.
I polled the other Mk II owners in our harbor (including valuable poster Chuck "pierview"), all with newer boats than mine, and they all report the same plumbing. I checked the manual for the pump (Jabsco 18590-2092, replacement for the original 185900-1000), and it says that an underwater outlet must be plumbed through an anti-siphon valve above the waterline. It actually has a nice diagram!
Unless I'm missing something, this is very surprising. The engine raw water intake, head flushing water intake, and shower sump overboard have loops. The only other overboards that don't are the sinks, but I think the top of the galley sink is above the waterline.
Am I crazy, or what am I missing? I feel I must install a vented loop on the macerator overboard to prevent possible sinking. Has anyone done this, and if so would appreciate any advice or lessons learned.
(I searched the archives without finding anything directly on point.)
Joe & Patti Worth
"Tehani"
1999 C36 MKII #1810
Atlantic Highlands, NJ
There is supposed to a 3-way valve to switch between overboard valve and pump-out hose. This valve will also prevent flooding assuming you do not have any leaking hoses.
I had to add the 3-way valve after the macerator pump section broke and unspeakable filled the bilge.
There is no siphoned break between macerator and overboard valve - that is a good idea of course.
Sail La Vie 1999 Catalina 36 MKII, M35B-17031, Coyote Point, San Mateo, CA
About Sail La Vie
Joe,
There is a simple reason why there is not an anti-siphon valve between the macerator and the thru-hull. The thru-hull should be closed (and/or locked) at all times, except when in use emptying the holding tank. You should not be sailing or motoring or even sitting at the dock with the thru-hull open. Sea water can and will back-flow into the holding tank if the thru-hull is left open. AND, it is illegal to discharge within three miles of shore, plus many "No Discharge" coastal areas. All of the other thru-hulls you mentioned above are designed to be left in the open position (except when you leave the boat, for obvious reasons) while the boat is in use. Hope this helps.
Tom Sokoloski
C36/375IA Past Commodore
Noank, CT
Thank you Tom. I will second your post.
Randy Sherwood
Mutualfun 1990 # 1057
T/R W/K M35a
Home. Charlotte, Mi.
Boat. St Augustine,Fl.
I believe Joe's problem is that the valve "showed" as being closed but the valve itself was broken so that it was slightly open causing the back flow so, locked in place or not, sea water was coming in.
Chuck Parker
HelenRita 2072 Mk II
2002 Tall Rig - Winged Keel
Atlantic Highlands, NJ
Thanks for your replies so far!
Chuck is correct that the overboard seacock failed, thus allowing the backflow without the safety of a vented loop.
I can see that adding a three way valve, per Haro, would add an additional valve between the sea and flooding the boat. That three-way valve could also fail, could it not? However, a vented loop is virtually fail-proof, as long as you inspect it annually for blockage.
Still wondering if anyone else has added a vented loop in the system?
I've also attached a diagram from West Marine that shows the exact same set-up we have, plus the vented loop.
Joe & Patti Worth
"Tehani"
1999 C36 MKII #1810
Atlantic Highlands, NJ
On our boat, there IS -- just as in the West Marine diagram -- a loop for the line that runs to the direct overboard discharge (it goes up behind the port cabinet and then back down under the settee to a 1.5" seacock. That line is accessed by a 3-way diverter valve, inline before the tank, which selects between waste going to the tank vs going directly overboard (we've used so rarely -- only on long well offshore passages -- that it generally gets totally frozen, even after I replaced it within 6 months it was frozen again; its just easier to use the macerator instead).
Not sure I'd want a vented loop inside the boat (as depicted in the West diagram), would be a rather smelly addition!. If you wanted a failsafe, a simple solution would be perhaps a second ball valve in the line to the macerator would be better -- as Tom indicated, this line should normally be shut anyway, rather than left open, so why go to the trouble of adding a loop?. And by the way, diverter valves -- besides tending to seize up quickly in this application, generally don't seal as well as a simple on-off ball valve, so I'm not sure that would be much of a backup either.
Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY
Thanks, Matthew! I did read that if you do have a vented loop in your sanitation overboard line, the vent should also be hosed to the outside, to prevent the smell problem you accurately describe!
Joe & Patti Worth
"Tehani"
1999 C36 MKII #1810
Atlantic Highlands, NJ