Holding Tank Troubles

Jul 9, 2015
20
Catalina 34 Mk II Toronto
Does anyone have experience with holding tank contents slowly backing up into the head? I pump out the head and put some fresh water in it...several hours later it seems that some of the holding tank contents have slowly seeped back into the head. is there a one-way valve that might need to be replaced?
 
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
Yup, it's called the joker valve. It's at the base of the pump if you have the Jabsco head, where the effluent hose starts. If you are a seasonal sailor it really should be changed annually.

Also, you could have back pressure building up in the tank and lines due to a clogged vent line. This is common on sailboats especially older Catalinas that use a stanchion as a vent.

Check out the C34 IA Tech Wiki. They have lots of info for your boat. You should also consider joining the C34 IA. Great group of guys, most notably Stu Jackson who is the group secretary and posts here regularly.

Good luck and fair winds,

Jesse
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
If you get a rebuild kit it will come with a lot of parts you don't need and will cost almost as much as a complete new one (for the Jabsco model anyway). Try to find just the joker valve, and brand doesn't really matter, they're all pretty much the same. And do check the vent, one time filing the tank all the the way up will plug the outlet fitting. On a lot of boats they use fuel vent fittings which have metal screens to keep sparks out, those can be removed on a waste tank to lessen the clogs.
 
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
If you get a rebuild kit it will come with a lot of parts you don't need and will cost almost as much as a complete new one (for the Jabsco model anyway). Try to find just the joker valve, and brand doesn't really matter, they're all pretty much the same. And do check the vent, one time filing the tank all the the way up will plug the outlet fitting. On a lot of boats they use fuel vent fittings which have metal screens to keep sparks out, those can be removed on a waste tank to lessen the clogs.
I would disagree that brand doesn't matter. There are big differences in performance. For actual use performance the Jabsco is far superior to the other major brands. But you will need to do some extra steps during winterization.

I would recommend you read the testing done by PS.
 
Sep 23, 2009
1,456
O'Day 34-At Last Rock Hall, Md
Correct, the one way valve is called a joker valve and should be replaced every couple of years.
However, as I believe Peggy, our Headmistress, has pointed out, your holding tank cannot possibly "back up". The hose into the tank is all the way at the top. So unless it is overflowing into the vent and the intake hose, it cannot go against gravity.
Make sure you are fully pumping out the hose into tank and install a new joker valve.
Also get a hold of the book "getting Rid of Boat Odors". Lots of good stuff there.
Good luck.
 
Dec 2, 1997
8,171
- - LIttle Rock
Does anyone have experience with holding tank contents slowly backing up into the head?
Unless the holding tank is so full it's overflowing, there's no way that tank contents can back up into the toilet because the head discharge line is connected to a fitting at the TOP of the tank, and last I heard, sewage can't jump. So the bowl contents aren't getting to the tank.

Three possible causes:

1. a blocked tank vent. When air in the tank displaced by incoming waste can't escape out the vent, the tank becomes pressurized, creating backpressure that won't allow flushes to get to the tank. If a blocked vent prevents air from replacing tank contents as they're pumped out, the pump or overboard discharge pummp will pull a vacuum that won't allow more than about a gallon to be pulled out...in which case, your tank just might BE full to overflowing even though you think it's been pumped out. If you've noticed that a manual toilet is getting harder to pump, or an electric toilet has started "burping" and spitting up after each flush, that's almost a guarantee that your tank vent is blocked. A new joker valve won't help.

The most common location for a vent blockage are the vent thru-hull and the vent line connection to the tank, both that end of the hose and the fitting on the tank.

The cure: Clean out the vent thru hull and the vent line connection to the tank.

2. The toilet discharge hose runs up and over a loop (not necessarily a VENTED loop), or it's just an uphill run from the toilet to the tank inlet fitting...and since water runs downhill, that's what it's doing...because you aren't flushing in the dry mode long enough to push the flush over the top of the loop or get the flush to the tank. A new joker valve may prevent the back flow from making it into the bowl, but only for a short time...until enough flushes stretches the slit open. However, joker valves in manual toilets should be replaced annually, or at least every two years, because they're essential to the efficient operation of the toilet. Find the article titlled "Joker Valves 101" in the Sanitation and Plumbing forum archives for the explanation of what a joker valve REALLY does.

The cure: learn to flush longer in the dry mode. Few people realize that any manual toilet that's working anywhere NEAR factory spec can move bowl contents up to 6 linear or 4 vertical feet in the dry mode. Learning how to use the dry mode to do more than just push the flush out of sight can increase the number of flushes your tank can hold by up to 50%.

3. A blockage in the head discharge hose...either sea water mineral buildup in it has reduced the diameter enough to all but block it, or somebody flushed something they shouldn't have.

4 A combination of any or all of the above.
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
If the tank is above the toilet like mine is, there's a lot of liquid left in the hose. I figure mines at least two gallons. Add pressure from a clogged vent and it can seep back pretty bad.
 
Jul 9, 2015
20
Catalina 34 Mk II Toronto
Peggy (and all) - thanks for the detailed explanations. I think it may be a blocked vent with pressure building up...seems consistent with my problem.
 
Dec 2, 1997
8,171
- - LIttle Rock
Geoff, if--as is the case on a lot of Catalinas--your tank vents into a rail stanchion that has a few TINY little holes in it, you'd be smart to relocate it to a new thru-hull fitting in the hull right below the toe rail, 'cuz those little holes are always clogging up with pollen, dust and/or any waste that spills out the vent when the boat heels or you overfill the tank. And as long as you have some work to do on the vent anyway, this would be a great time to do that.

Don't use a "vent" fitting...instead, use a plain ol' thru-hull--a "bulkhead" or "mushroom" thru-hull (see attached photo). This will let you prevent future vent blockages by putting a hose nozzle up against it and back flushing the vent line every time you wash the boat. People will claim that spiders and other bugs can plug up the vent, but that's not as common as some people think...and even if it does happen, being able to backflush it gets rid of 'em.

As far as I know, Catalina is the only boat builder who does run vent lines into rail stanchions, and while it's prob'ly a good idea for water and fuel vents, it's not for waste tank vents...and Catalina seems to have "seen the light"...'cuz on later model larger boats (not sure what they're doing now on smaller ones), they've begun using thru-hulls for waste tank vents.

(I think my photo shows a nylon thru-hull...I posted it just to show the type of fitting. Do NOT use nylon...UV turns nylon into powder.)
 

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Jul 9, 2015
20
Catalina 34 Mk II Toronto
Peggy - thanks again. I am quite sure its a blocked vent. I will take your advice and look at installing a new thru-hull. in the mean time, I will look at clearing the vent (I was not aware it was vented in the stanchion, but I just looked it up in my manual - shows me which stanchion but makes no reference how to service it. is it fairly easily done? FYI - just ordered a copy of 'Gid Rid of Boat Odors' from Amazon.
 
Dec 2, 1997
8,171
- - LIttle Rock
Holes are on the aft side of the stanchion...use an ice pick--or whatever fits--to open up any that are blocked.

I'd open up the deck pumpout cap to relieve any pressure in the system before removing the vent line from the tank. Warming the hose a bit with a blow dryer will make it easier to pull it off the fitting. Warming it again--WARM, not melt!--then lubing with a little Dawn or other dishwashing liquid will help you put it back.

Relocating the vent to a thru-hull will eliminate the need to ever go through all this again. Worst case, you might have to clear a mud dauber nest out of the thru-hull in the spring (you might want to add that to your spring recommissioning list)...you can do that with a screwdriver blade, then flush out the line.

Thanks for buying my book...if anyone else decides to get one, the online store right here sells it, and you'll be support the site.
 
Jan 19, 2010
968
Catalina 34 Casco Bay
I moved my head vent from the stanchion to a transom mounted vent. Now the odors associated with pumping the head are discharged astern and carried off in the wind. I always wanted to meet the marine engineer who placed that vent upwind of the cockpit...
 
Dec 2, 1997
8,171
- - LIttle Rock
Nothing wrong with putting the vent upwind of the cockpit...running it into a rail stanchion was the bad idea...ok for water and fuel vents, but NOT for waste tank vents.

A larger diameter short straight vent line to a thru-hull directly below the stanchion and the right kind of tank product prevents tank odors. Running it all the way to the transom just gasses the people downwind of your stern.

You'll find a lot of information about how to PREVENT tank odor out the vent if you search the archives of the plumbing and sanitation forum.
 
Sep 15, 2013
697
Catalina 270 Baltimore
From experience I can tell you to check and clean the tank vent before you do anything else. A clogged vent can do a lot of nasty things including having the effluent blow up all over the poor dock hand's face while emptying the tank. That one cost me a big tip.