cold weather lesson - drain valve freezes

ChanW

We had a rotten little lesson this spring driving back from NM (warm) into the great northeast (cold).

Because the black tank is inside the Tab, I (stupidly) forgot that its drain pipe and its valve are out in the cold, and perfectly susceptible... When I saw the seeping hairline crack in the valve body once the weather warmed up, the 'duh!' lightbulb appeared over my head.

So, just a heads up, make sure your black tank is emptied and then winterized with a bit of antifreeze, before you head back north!

DurangoTaB

Chan...can you be more specific about where the crack was?  I'm wondering if putting some pink stuff in the tank isn't enough to protect the valve, and maybe we should drain a little pink out to winterize the valve...

Nomad

The last time I did it, I poured some pink into the toilet/black water tank, then pulled the drain valve a bit to release some into the end cap area. Was in 10 degree weather without any harm. Disclaimer: You're mileage may vary.

ChanW

Durango, it was in the part of the valve that the 'gate' slides into when you pull the handle. In the picture below it would be in the right hand section, but closer to the pipe than to the handle. 

I was wondering the same thing, but I think if I had drained it thoroughly, before I'd added antifreeze, the only thing in there would've been the antifreeze.

jkjenn

Chan, given plastic's susceptibility to crack, is it possible that the temperature changes could have caused the crack, even with anti-freeze?

ChanW

I don't know Jenn. I was pretty cavalier about leaving the stuff in there til the weather warmed up, thinking how the black tank is in a heated space (I left the heat on in the Tab when we got home). And that part of the valve doesn't have much mass to hold the heat - the valve is pretty thin there.

The temps on the road were actually pretty mild daytime temps, but when we got home, we had below freezing for a few days, I think. Dumb me.

But it is just a hairline crack, can't really even see it unless it's seeping, so I should be able to patch it with something, maybe PVC cement.

DurangoTaB

Chan...with that kind of plastic, I'd suggest using epoxy made for plastic...

ChanW

Durango, thanks for the suggestion.Yeah, I was thinking about epoxy.

I've used marine epoxy in marine (wet) situations, good for plastics, metal, wood, fiberglass, and this is kind of wet (ewww).

Then there's JB Weld, which is (amazingly) still holding my tractor PTO case together, but I s'pose that's a metal application.

I was thinking that the plastic that's cracked might just be PVC, like the pipe it's attached to, and PVC cement actually dissolves the plastic a little, so I might be able to sort of weld it. I'll test it on a safe spot first, see how it works. If it doesn't work I can always go over it with epoxy.

ChanW

Y'know, I looked at the thing a bit closer today. The gate valve is a completely separate unit. I'm thinking it'll be easier to simply replace the valve than to chance repairing it.

The plastic says ABS on it. Pushing on it tells me it's pretty thin (might be why it cracked).

Maybe I can find a higher quality valve unit.

Nomad

ChanW - Ya, that assembly is comprised of several PVC pieces. When I wiped out my gray water assembly, it broke by those nuts in the corners. watched the RV repair guy pick parts from his bins and replace. The black water has fewer parts than the gray. If I'd have had tools, I'd probably replaced it myself. Any good RV service/repair/parts place would have the components.