"Nuts" to Trap Adapters

Verdeboy

Verdeboy

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I've proven once again that the plastic nuts that come with p-traps do not work on trap adapters. Today I had to replace a 1 1/4" p-trap, and the nut that came with the p-trap did not tighten properly to the trap adapter. After a couple turns, it just loosened up again. I doubt I can find a deeper 1 1/4" nut, so is the only alternative to put a 1 1/2" adapter on the 1 1/4" trap adapter that is coming out of the wall and then use a 1 1/2" p-trap? I've found a deeper 1 1/2" nut that works for basket strainers and will probably work for 1 1/2" trap adapters as well.
 
plastic to metal trap nuts is never good.Use metal nut to desanko withplastic tube and you should be ok .Rector seal #5dosnt hurt.
 
If everything is right...which it should be... there should be no need for any pipe dope.
 
cwhyu2 said:
plastic to metal trap nuts is never good.Use metal nut to desanko withplastic tube and you should be ok .Rector seal #5dosnt hurt.
Click to expand...
I don't understand this. The P-trap is plastic, and the trap adapter that is already glued in place is plastic. Where does the metal nut come in?
 
usually when a plastic slip nut tightens and then loosens it's due to over tightening, cross threading, or damaged threads. plastic is easy to cross thread if your not carefull. most trap adapters come with the slip nut included, and that nut should be used.

on another note. While it may not be neccessary, I always use plumber's putty on the bevel washers on plastic traps. why come back if you don't have to.
 
I can't figure how plumbers putty will do anything on a slip nut.
 
BAPlumber said:
most trap adapters come with the slip nut included, and that nut should be used.
Click to expand...
Am I right in believing that the slip nut used for the trap adapter needs to be FIP threaded and is different from the threads on slip-nuts that come with p-traps? If so, can you buy this special nut separately, or do you need to buy a trap adapter just for the nut each time you replace a p-trap?
 
In my state, this topic is moot.
We use only 1-1/2" traps, those schedule 15 "dollhouse" traps are a no-no.
The most frequent reason for desanco nut failures on 1-1/4" tailpiece adaptors is when you use a 1-1/2" desanco (trap adaptor) with one of the 1-1/2" by 1-1/4" washers.
The washers are so thick you have to crank the nut to get them to hold, but then the plastic nut either cracks, or skips threads.
I use a 1-1/2" by 1-1/4" desanco with the smaller 1-1/4" nut & washer.
HJ and Cass are right, putty or dope aren't good on a desanco.
The washer itself should hold, if it doesn't and your depending on dope or putty, it may leak in the longterm.
Also, HJ makes a very good point, putty and many dopes are petrolium based, supposedly not good for PVC, though many of us use the dope anyway on CO's and threaded adaptors.
 
Grumpy, those are all great points. Unfortunately, this house was built in the sixties, and I am dealing with a plastic 1 1/4" trap adapter that may or may not have a bad thread or two. I simply need to connect my 1 1/4" p-trap to it and have it not leak.

I would have to tear into the wall and remove a cabinet to replace this old trap adapter, and I'd prefer not to have to do that.
 
Cass said:
I can't figure how plumbers putty will do anything on a slip nut.
Click to expand...

won't do anything for the nut.

hj said:
Plumber's putty should NEVER be used on plastic. I contains mineral oil which dissolves plastic.
Click to expand...

I've used putty on the nylon bevel washers that are used with pvc end, center waste and p-traps, with no recalls for the last ten years. the plumber who trained me on this also "says" he's never heard of a problem.
 
hj said:
Plumber's putty should NEVER be used on plastic. I contains mineral oil which dissolves plastic.
Click to expand...

I can't tell you how many plastic toilet supply nuts that have cracked and flooded peoples homes I have replaced.

Failure was due to either putty or dope being used on the plastic threads.
 
BAPlumber said:
won't do anything for the nut.



I've used putty on the nylon bevel washers that are used with pvc end, center waste and p-traps, with no recalls for the last ten years. the plumber who trained me on this also "says" he's never heard of a problem.
Click to expand...

Because you were trained that way doesn't make it right.

Please explain how it helps threads / bevel washer from leaking.
 
putty

Putty does not affect the nylon washers, it weakens the PVC or ABS locknut. In any case, if the locknut, regardless of the material, leaks it was not assembled properly or it is defective, or the fitting is defective.
 
I have seen putty on slip joints. Don't know if it ruined anything or not. I have never seen putty on a toilet supply connector! That guy must have been struggling! Those nuts certainly are susceptible to cracking, from overtightening, but I have more often seen the shank of the ball cock cracked, also possibly from overtightening.
I have also seen a lot of slip joint nut cracked, again possibly from overtigthening.

On the trap adapters, I believe they are straight pipe threads. I always thought the threads on slip joints were also straight pipe threads, but maybe they are not standard. Maybe this is where he problems arise??
 
jimbo said:
On the trap adapters, I believe they are straight pipe threads. I always thought the threads on slip joints were also straight pipe threads, but maybe they are not standard. Maybe this is where he problems arise??
Click to expand...

Unless it's some obscure hardware store special, the threads are IPS (NPT).
Desanco nuts fit right onto male adapters.
 
I guess the threads on that 1 1/4" trap adapter are a little messed up--probably the result of having a metal nut (overtightened) on the PVC threads for all those years.

I haven't had a callback yet, but if I do get one, I'm going to screw on a 1 1/4''-1 1/2" adapter with plenty of pipe dope and then glue on a 1 1/2" trap adapter to that and just use the nut that comes with the trap adapter.
 
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