C&C35 Mk III Head Flooding

[robbo64]

Hi there. I'm new to this forum so "hi" to everyone out there! We own a 1984 (Labbatts) C&C35 MkIII on Lake Ontario. When we get into relatively heavy weather, there is always backwash in the head and it sometime floods....yuck! I have tried closing the through-hull, locking the pump mechanism and have replaced joker valve regularly and the pump piston completely. All piping is new, the air lock is clear, the vent line is clear and the only suggestion I have is to create a larger 'loop' in the pipe. Any other ideas?

[rbk]

Sounds like you’ve answered your own question. Anti siphon isn’t much good when it’s below the water line. If space a s aesthetics are an issue try and draw a diagram more or less to scale and using a ruler and protractor ‘heel’ your drawing over to simulate heavy weather to figure out how low you can go; Or just plumb it as high as possible and be done.

[robbo64]

Thanks @rbk.......perhaps there are some other tricks, like putting a shut-off valve in the line behind the head in the event that I cannot get the loop high enough. Not sure if anyone has done that or if it is even possible!

[rbk]

Just re-read that and saw you e closed your thru hull with same results. What about your intake? Could have a leaky valve on the supply side?

[robbo64]

Thru-hull is the supply is it not? The outlet to the holding tank is where I think the problem lies as the water that floods is grey.

[peghall]

Welcome to the cruisers forum!



I don't think the source of your flood is the holding tank--for several reasons: 1. holding tank contents are typically brown, not gray...2. The inlet fitting on a holding tank is at or on the top of the tank, so your tank would have to be very full for contents to be able to run back to the toilet. IMO you need a vented loop in the toilet INTAKE. It should NOT be installed between the thru-hull and the pump (it'll interfere with the toilet's ability to prime), but between the pump and the bowl...6-8" above waterline AT MAX HEEL, which on most sailboats puts it 2-3' above the bowl. This will require replacing the short piece of hose the toilet mfr used to connect the pump to the bowl.

I'm guessing from your saying that you "lock the pump down" that your toilet is a manual Jabsco...Figure 1 on page 3 of the owners manual will show you where it goes. But whether your toilet is a Jabsco or not, the installation instructions for all manual toilet put the intake vented loop in the same place: between the pump and the bowl.


--Peggie

[endeavour55]

I have a 44 power cat. on this and every boat I have had I always replace my sani hoses with flexible PVC. It does take some time, but well worth the effort. While doing this I install a check valve from head to tank. the closer to the head the better. Once a year I have to take the check valve apart for cleaning, but always works great. and no more stinky head hoses.

[Dougtiff]

Flexable PVC pipe, whats that ?

[peghall]

The cheapest single wall sanitation hose....Shields or Trident #148. The least resistant to odor permeation.

--Peggie

[vanderd]

Hi Endeavour 55. I suspect we have the same boat (44 Trawlercat). I don’t know how to do a private message but if you do I would love to explore further what you did. Thanks, bvanderd

[thunderhoof]

I had a similar problem with my 2003 Beneteau 40.7. When sailing heeled over in heavy weather the Jabsco head would back fill. I replaced just the pump handle and top support with the newer "Twist and Lock" style. The problem seems to be solved since this style seals the output line when the head is not being actively pumped out.

I don't know if this fix applies to your boat but someone else might use this approach.

[pcmm]

Originally Posted by rbk

Sounds like you’ve answered your own question. Anti siphon isn’t much good when it’s below the water line. If space a s aesthetics are an issue try and draw a diagram more or less to scale and using a ruler and protractor ‘heel’ your drawing over to simulate heavy weather to figure out how low you can go; Or just plumb it as high as possible and be done.

C&C's ( and other boats of this era) often didn't have anti-siphon loops in the toilet discharge. How is your toilet discharge plumbed?

[Tetepare]

No matter what the joker valve should prevent backflow.

[Boatwright]

A lot of Great Lakes boats of your vintage have retrofitted holding tanks. These were often incorrectly plumbed by DYI owners.

See the attached Jabsco piping diagram. Pay particular attention to keeping the loops as high as possible. You do not need the anti-siphon valve shown for the discharge line to the holding tank. These are prone to clogging and you won't sink your boat from this source.

Consider using regular PVC drain pipe for the waste line, with short pieces of highest quality drain hose where necessary. Inexpensive hose will stink after a season or two.

[Boatwright]

Forgot the Jabsco instructions:

https://www.jamestowndistributors.co...t.do?docId=768