Rectorseal#5 vs Megaloc for PVC sink waste line

D107

Replacing a slop sink 1.5" P trap with PVC, advice received is to use a soft-setting sealant NOT a lubricant that could lead to overtightening. Rectorseal says it lubricates so my guess is for this purpose Megaloc is superior? Trouble is I already have Rectorseal around, and I'm guessing for experienced plumbers overtightening is not an issue.

Alan (California Radiant) Forbes

Just use the plastic, beveled slip joint washers supplied with the p-trap. No lubricant necessary or advised; they will make a mess of things.

EdTheHeaterMan

Use what you have. You are overthinking. ...anyway if you do overtighten it, you can get a new one at Home Depot... Save the receipt... Then you can return the broken one the next day.

But I never did that. that would dishonest and immoral. (but you will want to clean off the Rectorseal#5 from the fitting)

D107

Thanks all. Obviously there are different ways of achieving the same end. First photo below was my existing drainage, which employed a different setup than the other photos, which was recommended by the Home Depot plumbing dept guy. He said his method was 'stronger', and less connections. His method requires a soft setting thread sealer. I'll take EdTheHeaterman's advice and use the rector seal. I have the two-step primer and glue as well.

EBEBRATT-Ed

Just make sure whatever dope you use can be used with PVC. It will say it on the can

mattmia2

It is slightly larger than tubular waste. Unless you are bashing carts in to it or something, modern pvc tubular waste components are much more durable that the brass which gets brittle and wears thinner over time and eventually breaks if you aren't really careful about how you support it when you unscrew it.

D107

@mattmia2 Thanks, I never considered brass; it was PVC in either the style of the original setup or what's in the photos. Since no comment has criticized the new components choice I have, my question is: for the trap portion--see arrows in photo below--while it swivels on the trap output side (red arrow, under the union), above it --blue arrow-- the threads appear mis-threaded and do not turn at all within the union--is that by design? This is my first sink drain replacement, so for me it will be an accomplishment if I get it right.

Zman

They sure looks cross-threaded. That should be a union with tapered faces inside.
The parts you have selected should work fine although it is probably overkill of a utility sink.
I do my best to ignore plumbing advice from the guy in the orange vest.

@EdTheHeaterMan probably returned that one and they put it back on the shelf

mattmia2

Brass is mostly just used for looks where it will be exposed now. PVC is generally a far superior and less expensive product for most applications.

If you get that nut lined up right you should be able to get it to thread on all the way by hand.

D107

@Zman Yeah I think I'll return the stuff and go to a plumbing supply I know for a simple P trap with slip nuts maybe keep the straight piece; I think the Depot guy was also looking to sell me more stuff. So that mis-threaded piece should loosen freely right? Using all my force I could only get it move slightly. Mis-threaded would seem to present a leak hazard, rather than freely tightening into the taper.

EBEBRATT-Ed

@D107

That nut should thread easily on and off. If it doesn't return it

Alan (California Radiant) Forbes

https://www.youtube.com/watch?v=hzLqWu4DNO0

D107

@Alan(CaliforniaRadiant)Forbes Great video Alan, thanks!

D107

Last night I was able to muscle the mis-threaded union apart so at least I could do a dry run, which lines up perfectly. I will return that part though, since in the process--whoever originally channel-locked those threads like that--compromised them and left a lot of pvc shavings.

I can't blame the depot guy for that, I probably chose the piece myself without looking at the union closely. I think for a basement slop sink drain which is likely to get knocked around a bit, his thick PVC components were superior to those for a standard bathroom sink.

My only slight concern is that the male metal threads both under the sink drain and at the other end seemed to be made for slip nuts, so the threads only fill about half of the PVC female-threaded adaptor. With a slip nut, there would be outgoing pipe slipping inside the outer pipe to mitigate leak possibility. But I figure given low or no pressure line, some Rector-Seal5 pipe sealant and a tight connection I should be OK.

mattmia2

There isn' enough light to see how it connects to the system or to the sink but it looks like the connection to the system is a piece of copper with a male adapter sweated to one end and a compression adapter on the end that the wall tube goes in to.

I can't see enough of the sink to tell if that piece is a tailpiece or a tubular extension.

D107

@mattmia2 Correct Matt; originally connected by compression adapter but I'm using pvc female adapter with maybe 3/4" depth of threads, which mail adapter being only half the depth will not completely fill. Not optimal perhaps but I would think threads will keep watertight.

mattmia2

You will either have to unscrew that copper from the steel and screw a male adapter in to there, replace the compression adapter with a npt adapter, use a fernco, or use a tubular waste p-trap. You'll need a compression adapter for that tailpiece from the sink if you're going to go the pvc pipe route.

Alan (California Radiant) Forbes

My only slight concern is that the male metal threads both under the sink drain and at the other end seemed to be made for slip nuts, so the threads only fill about half of the PVC female-threaded adaptor. With a slip nut, there would be outgoing pipe slipping inside the outer pipe to mitigate leak possibility. But I figure given low or no pressure line, some Rector-Seal5 pipe sealant and a tight connection I should be OK.

The threads on that nipple are 1-1/2 NPT. The threads on the female adapter and the slip joint nuts are the same and are made to fit that nipple and thread size.

If you use a female adapter to connect to the iron pipe nipple, yes, you will need some kind of thread sealant like teflon tape or pipe dope. That's if you use the current p-trap that you originally purchased. However, if you use a tubular p-trap like in the video I sent, it uses slip joint nuts and washers in which case the threads don't make the seal watertight. In this case, it's the slip-joint washer that makes the seal and you won't need any sealant on the threads; it won't do a bit of good.

Yes, that is a heavier duty p-trap than the tubular one and probably a good choice for a slop sink. The threads on that union are often "sticky" and it can be very difficult to loosen that nut, even with a wrench. But it doesn't look cross-threaded.

mattmia2

The threads on the compression adapter are NPS.

D107

@Alan (California Radiant) Forbes Hard to tell from the photo but yes threads were badly cross-threaded by someone before me. Took all my strength while pushing in to free it--and then there were pvc shavings all over. I exchanged the piece for a new one that works fine. I agree they can be sticky--easy to see how someone with a channel locks can get in trouble quickly.

I tested it all with teflon on all threads and no glue yet in the three joint locations--only leak was from under the drain. So I'll glue that one first and then the others. About NPT or NPS treads I can't say. Here are more photos. Adapter seems to thread well onto copper--must be tapered since it tightens quickly.

If it turns out that this setup is incompatible, then the depot guy disregarded my photo which clearly showed a compression fitting setup.

Alan (California Radiant) Forbes

That's a fitting x female adapter that you screwed onto the trap arm. It gets glued onto another fitting, i.e. p-trap or coupling.

If you want to install a small section of pipe to reach the p-trap, you would use a female adapter:



And how will you connect to the sink drain? Another female adapter?

mattmia2

The compression adapter on the end of the copper pipe and the tailpiece connection on the sink are straight thread. they are not tapered and are too short to server as a watertight connection, they are designed for a straight thread jam nut only. the tailpiece connection is designed to seal to a flange on the end of the pipe with a gasket and the compression adapter is designed to seal to the side of the tube with a compression ferrule.

If you put enough sealant on it you might get the threads to seal, but they are too short to make a good mechanical connection, if it gets a decent kick it will just pull off the fitting. That is not how those fittings were designed to be used.

D107

@Alan (California Radiant) Forbes Yes, another female adaptor at the drain. @mattmia2 Interesting dilemma. Apparently if I wanted the harder thicker pvc setup I would have to redo the two ends for a long enough thread connection; otherwise I would re-do the existing setup in the thinner PVC. Both setups risk being dislodged by a jolt, so now that I've come this far perhaps I should just use the glue where required and see what happens. Not much $$ wasted here. In the future I would probably trust my local supply house more. Thanks for all your answers here.

mattmia2

You can unscrew that piece of copper, screw a male npt pvc adapter in to the stack and glue the pipe trap and a piece of pipe to the adapter.

You can glue a pvc compression adapter and piece of pipe to the inlet of the pipe trap and connect a tailpiece to the sink in to the compression adapter.

Alan (California Radiant) Forbes

@mattmia2 Yes, I now see those straight threads on the sink drain, but the threads on a compression adapter (we call it a trap adapter) are NPT, at least out West here.

Edit: Actually, when I look at the sink drain threads, they look tapered.

D107

I went ahead and worked with what I have and will keep an eye on things. Glue is drying now and I'll water test it a little later. Worst outcome I'll go back to metal--the original setup. When you do this like i have for the first time you get to appreciate the genius of mechanical systems developed over thousands of years.

rick in Alaska

Personally I do not like hard piped drainage like that. When it comes time to snake the line out, you have to take the union apart and then try to get your snake up and around the 90 before getting to the stack. If you used the tubular compression style trap, you can take it all apart, and have a straight run in to the stack. Just makes it easier.
Rick

ChrisJ

rick in Alaska said:

Personally I do not like hard piped drainage like that. When it comes time to snake the line out, you have to take the union apart and then try to get your snake up and around the 90 before getting to the stack. If you used the tubular compression style trap, you can take it all apart, and have a straight run in to the stack. Just makes it easier. Rick

I used a sch40 trap like that in my kitchen but have a female adapter on the line at the wall and a male on the trap side so worse case you can unscrew that connection.

But I also have a clean out right in the pipe a few feet away in the basement as well.

D107

@ChrisJ Thanks; got a pic of that setup?

mattmia2

Here is a trap adapter. It is straight thread, the micrometer is set the same in both pictures:



This is an npt adapter, it is clearly tapered:

D107

Thanks @mattmia2 and all for the education; the upshot of the job is that apparently the in-store advice was incorrect, but I went with what I had. When I first water-tested, there was some slight leakage at the end copper connection which might not have happened had I used a good thread sealant instead of teflon tape. So I wrapped that area carefully in grey hand caulking usually used for windows. Since then––and probably also due to natural internal drain debris filling any gaps––there has been no leakage at all. As a precaution I went out and bought a backup metal drain kit with the compression rings. Lesson learned and continued respect for the science of plumbing.

ChrisJ

Sorry I forgot to respond to your question.
I don't have any pictures handy, but there was nothing special. I glued a female NPT adapter onto the pvc drain pipe and then screwed the mating male adapter into it. It was just so things could be pulled completely apart without going into the wall etc.

Instead of trying to pack caulk on the outside of the leak why didn't you just unscrew the trap and then spin the rear piece back off? Surely there must be enough movement to get things to clear?

D107

@ChrisJ I think once the dry fit didn't leak and I glued the two pieces that needed gluing, and then it leaked, I didn't perceive that backing off was an option without other risks. The trap union threads on these things had already proven to be tricky--had to return the first one that was cross-threaded, probably by a prior customer who returned it indirectly into my hands--and the new one certainly had that cross-thread potential. So as an amateur, I cut my losses and ran with it.

ChrisJ

D107 said:

@ChrisJ I think once the dry fit didn't leak and I glued the two pieces that needed gluing, and then it leaked, I didn't perceive that backing off was an option without other risks. The trap union threads on these things had already proven to be tricky--had to return the first one that was cross-threaded, probably by a prior customer who returned it indirectly into my hands--and the new one certainly had that cross-thread potential. So as an amateur, I cut my losses and ran with it.

Sometimes knowing when to do that is the hardest part.
"Good enough" is very often better than what you'll get if you keep messing with it.........

mattmia2

The union is hard to cross thread if you pay attention to what you're doing. If it doesn't screw on several turns by hand, back off and realign it. You would have to use some channelocks or something to cross thread it.

ChrisJ

mattmia2 said:

The union is hard to cross thread if you pay attention to what you're doing. If it doesn't screw on several turns by hand, back off and realign it. You would have to use some channelocks or something to cross thread it.

I very often turn things backwards to feel them click.
I find it makes things easier to feel and less harmful, especially with plastic threads.

rick in Alaska

@Alan(CaliforniaRadiant)Forbes
The video was fun until he started putting it back together. He didn't put any primer on the pipe and then used teflon tape on the compresssion fittings, which wouldn't have been quite as bad if he had rolled it from the bottom of the roll, instead of the top.
And I don't know about anyone else, but I have never heard it called a marvel fitting. Trap adapter here also. East coast thing?
Rick