How to remove this!

[joker460]

The vent line from the holding tank broke in half at the tank connection.
I've tried some methods but the remaining fitting is sticking fast. Any ideas without damaging the tank which is plastic.
It's strange that the fitting broke. It's a fresh water boat.
Pictures attached.

 

[Peggie Hall HeadMistress]

Not strange at all...it's metal. Salt isn't the only thing that corrodes metal... moisture and air can do a dandy of turning metal into rust anywhere. If tank contents got into the fittings--which, judging from the "stuff" in the fittings in the thru-hull and the tank, it obviously has--urine is what destroyed the fitting. It's so corrosive that it makes salt appear benign in comparison.

All of which explains why a metal fitting should not only not have been used in a holding tank, but not in any plastic tank because metal and plastic have widely different thermal co-efficients (expand and contract at different rates and in different amounts)...that can result in a cracked tank in climates that have extreme temperature swings. So when you replace the fitting, use pvc or marelon, not only in the tank, but also at the thru-hull.

So now that you know what NOT to do, let's see if we can figure out how to get the fitting out of the tank so you can do it right. What have you tried so far?

 

[Ron20324]

Make lemonade from lemons. Make a bigger hole, increase the vent size. The vent does not (normally) need a shutoff valve.

 

[Bill Roosa]

Try collapsing it inside. If you can get channel locks or vice grip jaws on both sides (across the diameter) collapse it a bit and that should free it up to unscrew it. If you can only get the jaws on one side then try twisting it to partially collapse it and then unscrew it

 

[Mechone]

cam type pipe extractor use them all the time

 

[SG]

I suspect it's "treaded" from picture. Is that correct?

If the fitting doesn't have too much or too aggressive a sealant, then you could screw it "into" the tank.

Do you have an access plate that allows to reach the vent vent fitting -- or is the tank completely sealed?

Putting an access port into a plastic tank is unlikely to produce an easily sealed port. The plastic really want's to be heat bonded, and sealants generally don't seek to work very well. It's one thing to have a little fresh water leak out -- quite another thing to have a holding tank "expressing itself" or out gassing inside the boat.

Peggy....

 

[Peggie Hall HeadMistress]

Make lemonade from lemons. Make a bigger hole, increase the v

I was thinking along those lines too. If he can't get the rusted fitting to let go without destroying the threads (which would make it impossible to replace it with a new plastic thread/barb fitting), fill that one up with enough melted PE to seal it and put a new larger vent fitting in the tank using a Uniseal UNISEAL

Putting an access port into a plastic tank is unlikely to produce an easily sealed port.

Inspection/cleanout ports are actually very common in plastic holding tanks. SeaLand (now Dometic) even offers a DIY retrofit kit http://www.defender.com/product.jsp?path=-1|51|2234299|2234304&id=197164 No sealant needed...in fact, using sealant is a very bad idea because it doesn't work (you were right about that much!) Installation is easy: Use a hole saw to put a round hole in the top of the tank, put the rubber gasket down, then set the threaded flange down on the gasket. Self tapping screws secure it...a rubber o-ring seals the threaded cap. It does not leak, not even gasses. It's the same access port that SeaLand has always used for all their TankWatch tank level indicators and also for their "diptube retrofit kit."

 

[joker460]

I could drill it out. I like the cam idea , would have to see what sizes are available and the cost since I probably won't need it again(knock on wood).
It's in such an accessible location.
Peggy: This was a factory installation See Picture before it broke off. I will replace with a plastic fitting. Is it really necessary to put a ball valve in place? If yes, would it also be plastic?

 

[Peggie Hall HeadMistress]

This was a factory installation

Not much was known about sewage management when it first became necessary to install holding tanks...and some builders are still at the bottom of the learning curve. Most of the early holding tanks were aluminum...it's ok for water holding and inexpensive, so why wouldn't it be ok for sewage holding. It wasn't till the early '90s that they realized metal--even 316 stainless--was the wrong choice for holding tanks--that urine turns 'em into colanders--and began using rotomolded polyethylene tanks. Steel and bronze are pretty impervious to salt, so some builders used it for the fittings. But they're not impervious to urine either, it just takes longer to destroy 'em. Europe has been slower to get onto the holding tank bandwagon than the US, so both builders and installers are even further down the learning curve than most US builders. I've even seen UK tanks vented into cockpit lazerettes and chain lockers in a misguided effort to prevent odor from perfuming the air.

Is it really necessary to put a ball valve in place?

On a vent line? No. Seacocks are only needed on below-waterline thru-hulls.

Back to my question in my first reply: what have you tried so far in your efforts to remove the fitting?

 

[Ron20324]

...Peggy: This was a factory installation See Picture before it broke off. ...

Do away with that downward loop. Once the tank fills, it will flow into the vent hose and block it. Run the vent hose uphill, and flush it from the outside when you pump out.

 

[Peggie Hall HeadMistress]

I just took a closer look at that photo...that hose not only looks way too large to be a factory vent line, but it goes straight up, so I assumed it's the pumpout line. That would account for for the dip in it--which shouldn't be in the pumpout line either. Nor are any valves needed on the tank. I'm starting to think that all the tank plumbing needs a complete overhaul.

 

[joker460]

Update: Got the remaining fitting out using the pipe extractor (as mentioned by Mechone). Home Depot had then, $5.
Replaced with 1/2" Plastic Elbow, 1/2" nipple plastic, 1/2" Hose Barb plastic. No Valve.
Everything else works great.
Thanks for all the replies.