Keep trying to remove the trap arm, cut it, or give up?
January 17, 2013 4:21 PM   Subscribe

60-year-old house, trap arm and drain/vent are galvanized, trap arm is rusty and I want to remove it. Or should I cut it, or hire someone to do it for me?

After a leak, I'm replacing floor and some wall in a small bathroom, and the 60-year-old galvanized trap arm (well, the 4" pipe screwed into the drain/vent) is rusty inside (no surprise), with sink-end threads half-gone.

I have a new 4" galvanized piece ready to go, but I can't get the old one out. So far I've soaked it in penetrating lubricant and tried to wrench it off, but it won't budge in the slightest. The button board is already down, so I have good access to the drain/vent as well as the trap arm, although the incoming lines do limit wrenching room somewhat.

I've narrowed it down to four choices:

1. Keep soaking it and trying it over the next few days, with a longer wrench and a bar of pipe. Cost: $40 for the wrench, a little more for the pipe, and the frustration of having spent that money if I still can't get it off.

2. Try a torch and a plumber's candle, with those additional costs (as I have neither), and the same potential frustration.

3. Rent a sawzall with a metal-cutting blade and hack through the pipe, leaving an inch that I can attach a PVC adapter to. Beyond the rental cost, I'll still have an inch of rusty pipe that'll go bad someday, and I hate to make this a short-term solution.

4. Hire a plumber, who may do #1, #2 or #3 above -- I don't know which -- and will presumably charge me more than any other solution. If it gets the pipe out, and I wouldn't have been able to, then great, it's worth it...but if he's just going to cut it, that's an expensive price to pay for a short-term solution, and if there's a good chance I can get it off, I hate to pay the money.

So, my questions: have you ever gotten one of these off with heat and a plumber's candle, in a case where WD-40 didn't work? has lubricating for 24-48 hours ever gotten the pipe off when a few hours' worth of soaking didn't? Is cutting even an option, and if so, will a sawzall do it or do I need a pro?
posted by davejay to Home & Garden (11 answers total) 1 user marked this as a favorite
I don't know, but I'm favoriting this as I will need to do the same thing in a matter of weeks. We were just going to hire someone.
posted by checkitnice at 4:25 PM on January 17, 2013

When you say 4" pipe,, you're referring to the length and not the diameter, right?

What size pipe wrench do you have now?

Can you post a picture of the problem?
posted by jon1270 at 4:32 PM on January 17, 2013

In a house built in 1964 that we once owned, the kitchen sink trap was WELDED to the pipe in the wall. I learned many new words from the men who struggled to replace it.
posted by Cranberry at 4:46 PM on January 17, 2013

Best answer: If you are running into issues now, it will be easier in the long run if you just cut the rusted and ruined pipe out and replaced it with something new. You can cut it back as far as you can/need to and use a coupler to bridge the PVC to metal gap. It has saved me time over the years since it makes return trips to clean out traps much easier. The compression fittings easily unscrew, no rusted threads to deal with. You do not necessarily need a reciprocating saw. It can be done for cheaper if you get a good bimetal hacksaw blade and patiently cut the pipe by hand. It might even be easier if space is tight.
posted by Nackt at 6:13 PM on January 17, 2013 [1 favorite]

I don't know which of your options is the best, but if you really are using WD-40 as your penetrating lubricant, I would first soaking the area with something better - like Liquid Wrench, PB Blaster, or, my personal favorite, Kroil, then trying with your existing wrench.

I don't think WD-40 penetrates rust very well at all. Kroil especially has worked wonders for me with stubborn bolts.
posted by that possible maker of pork sausages at 8:01 PM on January 17, 2013

Best answer: Don't go the torch route without some serious respiratory protection & venting. The galvanized coating is poisonous as it burns off.
posted by mollymayhem at 8:43 PM on January 17, 2013

Response by poster: Okay. So I'm going to try Kroil with the existing wrench (16" handle if I remember correctly), and if that doesn't do the trick, bimetal hacksaw it is.

That gives anyone else a few more days to tell me I'm out of my mind for cutting it, before I cut it. And thanks for the heads-up, mollymayhem, no torch for me!

Cranberry: any idea how they finally got it off?
posted by davejay at 10:15 PM on January 17, 2013

PB Blaster works great for penetrating and freeing up stuck/rusted stuff. Let it soak overnight, though.

An old tech I used to work with swore by a 50/50 mix of automatic transmission fluid and acetone, for freeing up stuck bolts.
posted by xedrik at 10:29 PM on January 17, 2013

FWIW, the reason I asked for a picture was to make sure I'm understanding the situation correctly. I've disassembled some seriously rusted pipes, and never needed any sort of penetrating lubricant. Unlike the threads used on machine screws, pipe threads are designed to eliminate airspaces in the threads as they are tightened together, and then the plumber assembles them with pipe dope (or, these days, teflon tape) which lubricates and fills in any remaining voids. It's tough for penetrating lubricant to get into these threads, because there are no openings for it to get into.
posted by jon1270 at 2:50 AM on January 18, 2013

Best answer: Are you talking about the pipe stub that comes out of the wall, that the sink's drain trap connects to? And that it is 4" long, rather than 4" in diameter?

And I agree with jon1270- pipe threads are interference fit so they become pressure tight once they are tightened up. This means that penetrating oil can't get in, but also that the "inside" of the threads can't rust up like machine bolts can either.

The right way to do it is to use two wrenches if at all possible. You are probably not putting enough torque on the pipe because you can see or feel the rest of the pipes in the wall moving against your pressure and are worried that they will break. This is the right instinct, and the solution is to put a second wrench onto the tee that the pipe goes into so you can put backpressure to work against.

Also, when using a pipe wrench, the right way to adjust it is to make sure the wrench makes a three point contact. The pipe should rest on the arm of the adjustable part as well as the teeth of it. So you open the wrench up wide, slip it onto the pipe until the pipe contacts the rear of the wrench, and then adjust it until the teeth make contact. But not too tight- the wrench should be loose enough to slide if you turn the opposite direction. (That's the point of the teeth- they are angled to dig into the pipe when you turn in one direction, and slip in the other. Your torque on the handle makes the teeth bite into the metal.)

If the wrench is sliding on the pipe, then you need a bigger wrench with wider teeth.
posted by gjc at 5:30 AM on January 18, 2013

Response by poster: Confirming the pipe stub, and that it certainly does look like it will never come out, in particular considering gjc's comment regarding interference threads.

Based on what I'm reading -- and how impossible it would be to get a second wrench around the tee -- I'm going to go with wire brushing out the inside of the pipe, cutting it to about an inch past the threads, and smacking a coupler on it, either a temporary or a permanent one depending on how the inside of the pipe looks after wire brushing (the bad rust is all on the sink-side thread bottom, presumably where water pooled and/or the coating was damaged during installation.

Thanks, all!
posted by davejay at 3:45 PM on January 18, 2013

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