Head vent issues 1992 mk1.5

[WBev]

Happy 4th to you.  The admiral & I are currently on the hook.  Of course, mighty Murphy is with us.
Thes holding tank vents to a mushroom on deck near the pump out. No y- valve.  No macerator. Toilet to tank, tank to pumpout. Vent line from top of tank  to deck.
Couldn't pump a flush this morning.  Admiral says bowl is refilling every time she pumped through the night.  Tank offs round on top, lifting cushion.
Vent hose was clear when got it off.  Massive stink from tank gasses. Mushroom allows air in & out.  90 degree elbow seems to have a one way valve in it.  Can bellows thes tank & gas escapes with vent hose off.
However when try to pump from bowl it won't go. 
We have a "no" paper & no #2 rule, so not a clog in line.
The tank was way pressurized from pumping.  I am stuck.  Any suggestions?

[WBev]

Forgot to state the head itself is a jabsco with 1 year old  valve pump assembly.

[Jim Hardesty]

My guess, think it has to, would be that the vent is plugged somewhere.  I would start by removing the pump-out cap, that should relieve the pressure.  If there's a lot of pressure it may force the waste up and out.  Then just start looking for a plug in the vent.
Hope it's an easy fix.
Jim

[Jon W]

Sorry I have to ask - Are you sure the tank isn't full?

Like Jim suggested, open the deck pumpout cap to relieve the pressure in the tank. The tank shouldn't be bulging anymore. Is that what you're seeing? Keeping the cap removed, can you flush the toilet without backing up into the toilet? If so, the pressure was causing the backflush and you don't have a blockage in the main line. The joker valve should keep waste from backflushing into the toilet. It could be overpowered by the pressure in the tank so you may need a new joker valve. I would replace the joker valve when you get back to your slip.

With the tank bulging, sounds like the vent to me too. When you removed the vent hose from the tank, did any waste come out? Is the 90 deg with the one way valve you're talking about on the tank top for the vent? You checked the vent hose and it was clear, can you remove the one way valve on the vent elbow to make sure it is clear and working? Then check the 90 deg vent elbow itself. If the vent deck fitting is clear, the hose is clear, the valve is working, and the elbow on the tank is clear, the vent should be working.

[Noah]

The holding tank vents to a mushroom on deck near the pump out. No y- valve.  No macerator. Toilet to tank, tank to pumpout. Vent line from top of tank  to deck.

I am confused? You say vented "on deck" What kind of vent and where is it located? Hole in stanchion, mushroom on vertical side of hull???

[Bill Shreeves]

During my second season with the boat I learned the waste tank level warning light no longer worked when I was sitting on the bench over the waste tank and the admiral flushed the head.  I was being lifted up and down ever so gracefully.  This was the second Murphy visit that week because I was towed in to my brand new marina because my exhaust riser snapped off of the engine on the way from the old marina on the Jersey coast to Worton Creek, MD.  So, naturally, this was the end of June and getting very hot on the Chessy so, I had to pay to tow the boat to the pump out because I was afraid with it being that full, heat could build and over pressurize the tank leading to very unpleasant results.     Afterward, the vent was not plugged and I suspected the pressure needed to push fluid up the vent hose to be greater than the tank is designed for.


I happen to know today is a really hot one on the Magothy and I'd seriously consider getting the pressure relieved as soon as you can.

[Ron Hill]

WBev : Beside all of the vents, You might check and see if the Joker valve is "inside out" !! 
Also You might also check to see if the large flapper valve under the pump is working OK.

A few thoughts

[WBev]

Thank you for all the replies.   Here is the short version: insufficient ventilation for use of Raritan K.O.  Enzyme death.   I bought what was on the shelf without reading it. 

The longer version: Removing the pump-out cap (carefully & with a towel over it) did nothing to relieve the pressure in the tank.  Bubbles were coming up in the toilet bowl, with noises. The deck mounted mushroom vent checked clear, as did the hose, but the hose did have "water" in it, likely from the pressure pushing it up. The elbow on the tank top was clear.  The water in the vent line made me believe it could be a water lock, preventing the vent from working.  Trip to a nearby marina for pump out on Friday, and added more KO w/out knowing it was the culprit in my poorly vented system. By Saturday morning we were getting bubbles again. Another marina visit. & pumped out right away.  Planned on addressing this after vacation with either new everything (because I couldn't find a clear problem), or a composting toilet.  On way home, the Admiral told me she read the bottle of KO and it said for use in well ventilated tanks.  Clearly, ours is not.  I hope this was the problem.

Of note: The mushroom vent is on deck, just forward of the pump out. No stanchion vent.   The 3/4" vent hose must dip lower than the top of the tank to get to the side of the hull, due to the fiberglass interior pan. That's why I thought a water lock was the culprit. I see no way around this.  There just isn't clearance.  To cut the fiberglas will put the vent line on top of the cushion. Same if I run a forward line as Peggy Hall suggested on this message board.