Holding tank full, not exiting through stanchion

[galway2004]

We have a 1984 Catalina 38, still figuring out plumbing / head set up and some unique issues for how it was set up prior to buying it.

Last week, our holding tank was full, but when we pumped the head the excess was not exiting through the port side stanchion. However, when we shot water down the stanchion, it would run down the vent hose. So there is no block in the vent hose. The excess had previously exited through the stanchion so this is first time we had problem.

Is this as simple as there being a clog between the head and holding tank? Anyone else had a similar problem? Wondering what I am missing. Thanks all

[capt jgw]

First, you should never let the tank get full enough to come out the vent. Besides the yuck factor, that is real likely to plug the vent. That usually occurs at the vent outlet, but also can clog the vent hose attachment to the tank. That might be your problem. Try blowing air or water under pressure down the vent hose to clear the clog. Not too much though, you don't want to pressurize the tank itself. Be aware that if the tank gets that full again it may reoccur.

[Orion Jim]

What is this “stanchion” of which you speak?

[wyb2]

A lot of Catalina’s have the holding tank vent integrated into one of the deck stanchions, with a hole drilled in the stanchion base and bit of tube welded to the bottom, and another hole drilled somewhere on the stanchion.

But yeah, echo post #2, you shouldn’t be relying on the tank overflowing to tell you when it’s full. As mentioned it’s likely to clog it, but also, that’s 3-4 ft of head pressure you are applying to the (plastic?) tank that isn’t really intended for pressure. That creates a non-zero risk of the tank bursting.

Plus our stanchion vent faced inboard instead of overboard, which seemed like and unnecessarily cruel design detail.

[capt jgw]

Originally Posted by wyb2

A lot of Catalina’s have the holding tank vent integrated into one of the deck stanchions, with a hole drilled in the stanchion base and bit of tube welded to the bottom, and another hole drilled somewhere on the stanchion.

But yeah, echo post #2, you shouldn’t be relying on the tank overflowing to tell you when it’s full. As mentioned it’s likely to clog it, but also, that’s 3-4 ft of head pressure you are applying to the (plastic?) tank that isn’t really intended for pressure. That creates a non-zero risk of the tank bursting.

Plus our stanchion vent faced inboard instead of overboard, which seemed like and unnecessarily cruel design detail.

Yeah, the first time I saw that I thought "what idiot designed this?" I can understand a prior owner pulling a dumbass move, I'm sure the present owners of my old boats agree, but the original builder? Come on now.

[Shanachie]

Aah, where to begin? I'm trying to decipher your post ...



Your holding tank system probably has a macerator pump or a hand pump designed to empty the tank through a through hull.


To empty the tank, open the lever on the through hull and pump. Note: the pump next to the head is not the correct pump. That only sends waste TO the holding tank.


If it doesn't have a pump connecting the holding tank and a through hull, that means the only way to empty the tank is to go to a pump-out facility, probably at a fuel dock, and have them show you how to do it.


There should be a cap stamped WASTE near the stanchion. That has to be opened for the pump out to proceed. The pump-out station will insert a hose into the opening and pull out the waste.



The opening on the stanchion is probably the air vent. You do not want to empty the holding tank through it. For one, it's too small. Two, the waste would be all over your deck.


It was easier, but more polluting, during the days of the old oaken bucket.

[peghall]

Yep. Catalina ran all their tank vent lines into a rail stanchion that has a slit in it at th bottom of the aft side of it for several decades, beginning long before holding tanks existed. It makes sense for water and fuel tank vents because it keep sea water out of fuel and water tanks. And when holding tanks came along in the 80s they saw no reason to vent them any differently. Fortunately after a couple of decade3 of complaints about clogged holding tank vents they finally started routing holding tank vent lines to thru-hull just below the toe rail. Fuel and water tanks still vent out a stanchion on the gunwale of the cockpit.


--Peggie

[peghall]

Stanchions are the uprights on which the rails sit.



--Peggie

[peghall]

Plus our stanchion vent faced inboard instead of overboard, which seemed like and unnecessarily cruel design detail.


Apparently a PO rotated the stanchion at least 90 degrees, 'cuz it should have aimed aft directly aft or overboard.


--Peggie

[peghall]

As others have already said, allowing the tank to get so full that it overflows out the vent is a major no-no. A tank level indicator will solve the problem. SCAD tank monitors Scad Tank Monitors are top rated, reasonably price, easy to install and (assuming your tank is plastic) use sensors that are attached to the outside of the tank, so they never clog.


I'll be glad help you figure out your system how it all works and how use and maintain it if you'd like to contact me directly. (click on my name at the left of my posts to send me a PM or an email).


--Peggie

[wyb2]

Originally Posted by peghall

Plus our stanchion vent faced inboard instead of overboard, which seemed like and unnecessarily cruel design detail.


Apparently a PO rotated the stanchion at least 90 degrees, 'cuz it should have aimed aft directly aft or overboard.


--Peggie

Hmm, the stanchion was definitely in it’s original orientation. One of the welded base styles where the mounting holes form a trapezoid.

I think I remember a round hole facing directly inboard. I know it wasn’t overboard, because I remember the one time we did overflow it, and sprayed sewage onto the sidedeck. Fixed that by drilling a new hole outboard and slightly higher, and covering the old with a hose clamp and chunk of vinyl tubing (well, and by not overfilling the tank).

Maybe a replaced stanchion. The boat was 32 years old when we got ahold of it.