Vent pipes

[Bob S]

I've been searching the archives for info on replacing or clearing a blocked vent pipe. Both the toilet and water tank vents are blocked. Could be a symptom of being on the hard for many years. My boatyard complained of an eruption when pumping out the waist. Ijust removed the vent pipe from the holding tank and tried an air hose 60lbs pressure and couldn't remove the blockage. i traced the vent up to a stanchion. I will have to remove a medicine cabinet in order to get to it. It looks like clear PVC tubing. I can't see how it's attached to the stanchion. Are there any tricks? Will I have to remove the stanchion from the deck? Stinky job!

 

[Bob S]

BTW

The boats a 1995 Catalina, not sure what kind of toilet it is but it is a manual pump.

 

[Maine Sail]

A blocked vent line is usually caused by over filling the holding tank. Over filling the tank forces the effluent up into the vent hose where it dries and hardens especially if there is a low spot in the line. On Catalina's they used a stanchion as the vent and many times that can be reamed out, with an electricians snake and from the deck side by snaking back towards the tank..

That hose is just held onto the stanchion with a hose clamp and the vent hole is on the inboard side of the stanchion about 2-3" off the base plate.

The fresh water vent may be a rusted screen. On many Catalina's they used Perko chrome plated zinc vents for the water tanks. These vents usually have a screen in them of a dissimilar metal and they can corrode and plug. Also any bleach in the tanks that got over filled and came in contact with chrome plated zinc vents will also, over the years, lead to corrosion issues. My guess is that it's the vent its self that is plugged or corroded.

Image Courtesy of Catalina Direct (LINK)

 

[sailingdog]

Bsmith-

May not be attached to the stanchion at all. It may just run up into the stanchion.

BTW, I doubt it is a result of being on the hard for to many years... without constant water flow through the vent there is very little chance that the water tank vent would clog from mineral deposits. More likely, the vent is clogged by insect activity... wasps love making nests in vent piping..

The holding tank hose is probably the result of overfilling the waste tank... since it would back up in to the vent at that point..and it is very likely to clog the vent hose.

Just curious, what evidence did they give that the fresh water tank vent is clogged. The waste erupting is pretty clearly a sign of a holding tank vent issue...but would indicate nothing about the water tank. The two tanks have, hopefully, isolated and separate vents from each other... if not, they should.

 

[Bob S]

Water tanks

Dog,

During the season I had to add water very slowly or it would backflow out the water inlet. First time this happened I went crazy with the water pump. Thought I had a hole somewhere in the line. I spent an afternoon trouble shooting before I realized the tanks where empty. And I just filled them
I'm sure Maine Sail is right. I will trace the vents back until i find the block. I was going to replace the waste vent with PVC tubing. I will ream the stanchion if I have to. How hard is to remove the stanchion?

Bob

 

[Peggie Hall HeadMistress]

Check vent thru-hulls first

That's where most vent line blockages occur. Scrape out what you find with a screwdriver or anything that'll work. If there's a screen in the thru-hull, knock it out...it's not serving any useful purpose.

Waste tank vent can also be blocked at connection to the tank, both the tank fitting and that end of the vent line...remove the hose and scrape it out.

Also check vent lines for any sags where water or waste can collect and cause a blockage and any kinks. Shorten, straighten as necessary to fix it.

If your waste tank vents into a rail stanchion, now would be a good time to move it to a real thru-hull, 'cuz the slit in the stanchion is so small that even dust and pollen can clog it. You want a waste vent vent thru-hull that'll allow you backflush it with a garden hose nozzle every time you pump out and or wash the boat to keep it clear. If you can get to the tank easily, leave the existing vent line where it is--just cut it off where you can reach it and put a plug in it--and run a new one to a location that doesn't require taking the boat apart to access it. You should replace the clear hose with sanitation hose anyway.

To keep water tank vent clear, overfill the tank to let water run out the vent.

 

[sailingdog]

Well, that's pretty clear evidence of the water tank vent line being clogged.

Dog,

During the season I had to add water very slowly or it would backflow out the water inlet. First time this happened I went crazy with the water pump. Thought I had a hole somewhere in the line. I spent an afternoon trouble shooting before I realized the tanks where empty. And I just filled them
I'm sure Maine Sail is right. I will trace the vents back until i find the block. I was going to replace the waste vent with PVC tubing. I will ream the stanchion if I have to. How hard is to remove the stanchion?

Bob

 

[Bob S]

Peggie,

Where does one put a new thru hull for a vent pipe? I would assume it would be topside. I checked the barb OD on the tank and it's 5/8. It's not blocked at the tank. The tube runs to a stanchion with a 3/16th hole in it's side. I tried to use a small piece of welding wire to open the tube but it's to hard a bend. I think I need to remove the stanchion. unfortunately I just had a new Fairclough cover installed for the winter.

 

[Peggie Hall HeadMistress]

Put it right below the toe rail

Anywhere you can get to from the inside. Ideally the line from the tank should be < 5' long and straight, but it may have to be a little longer.

Plan B: Enlarge the slit in the stanchion. You should be able to clear out whatever has clogged it using a small flat head screwdriver or a pocket knife blade. Then use the proper tool to cut SS to turn the slit into a decent size hole. If you don't have a metal cutting tool, someone you know or the local boatyard will...and with the right tool, it's a 5 minute job.

Not the ideal solution, but the simplest and it will solve your problem.

 

[Steve Dion]

Why not just drill a hole in the hull and put in a new hose and thru hull vent fitting.

I would suggest that you use one that can be back flushed each time you pump your tank.

 

[Bob S]

Peggie,

i bought your book. I will try drilling the hole in the side a little larger. Maybe it might be better to add a hole on the opposite side. I don't want to weaken it.

Steve, I've read a lot of the archives and see you had a similar problem. I also saw issues of vent location and boat heeling. That is why I was asking for a location that would be best if i decided to reroute the vent.

Bob