How to connect a PVC elbow to metal drain?

[Plubit]

This is my first adventure into plumbing and I need some guidance. This is in a 1940's home where a previous owner used one of those wonderful Form N Fit extensions to get the bathroom sink drain lined up with the P-trap that is angled slightly to the left in the photo, while the drain is off to the right side. I'm thinking a 1.5" PVC 45 degree elbow will get me pointing in the right direction so I can remove that Form N Fit abomination. I plan to attach a 1.5" to 1.25" PVC trap adapter to the elbow to accept the sink P-trap.

The white pipe in the photo is the output side of the existing P-Trap. I want to remove the existing P-trap completely and connect a 45 degree elbow as close as possible to this metal pipe. Then, I will connect a new P-Trap into the elbow.

When disconnecting the sink drain and moving the pipes around, I noticed a little water drip from the bottom of the metal nut. Perhaps it was the movement or an old washer behind the nut. I'm unsure how I should best connect the 45 degree elbow to the metal drain pipe. The P-trap output in the photo appears to be connected with a simple slip joint (washer and metal nut).

Should I use a new slip joint (washer and nut) to connect a pipe into the metal drain pipe or is there a better or more preferred method for connecting to the metal drain pipe in the photo? If a slip joint is appropriate do I need to use a metal nut or would a plastic nut be fine?

I would greatly appreciate guidance so that I can complete this first project.

 

[hj]

What is a "Form and fit" connection? All I see is a standard trap adapter with a PVC trap into it.

 

[Sponsor]

 

[Reach4]

There are slip joint elbows available in 45s and 90s.

You cut off the existing white pipe 1.5 inches or so away from the trap adapter. Screw on the slip joint elbow.

Alternatively, get a metal or plastic slip joint double off-set and cut it. Stick the cut end into the trap adapter instead of the current white pipe.

 

[Plubit]

What is a "Form and fit" connection? All I see is a standard trap adapter with a PVC trap into it.

The Form N Fit item is an accordion style pipe that bends and expands. It is not in the photograph I posted.

 

[Plubit]

Reach4: I appreciate the response. I wasn't aware there were double sided slip joint elbows. I didn't see those at Home Depot or I overlooked them.

Should I use a new slip joint (washer and nut) to connect a pipe into the metal drain pipe or is there a better or more preferred method for connecting to the metal drain pipe in the photo? If a slip joint is appropriate do I need to use a metal nut or would a plastic nut be fine?

 

[Reach4]

Reach4: I appreciate the response. I wasn't aware there were double sided slip joint elbows. I didn't see those at Home Depot or I overlooked them.

https://www.homedepot.com/p/Everbilt-1-1-2-in-Plastic-45-Degree-Slip-Joint-Elbow-C9665/205153648

Should I use a new slip joint (washer and nut) to connect a pipe into the metal drain pipe or is there a better or more preferred method for connecting to the metal drain pipe in the photo? If a slip joint is appropriate do I need to use a metal nut or would a plastic nut be fine?

I would use the one that is there. You could leave the pipe that is there now in place, and cut the pipe with a fine-tooth hacksaw or use a cutter made for cutting plastic tubing.

 

[Plubit]

https://www.homedepot.com/p/Everbilt-1-1-2-in-Plastic-45-Degree-Slip-Joint-Elbow-C9665/205153648

I would use the one that is there. You could leave the pipe that is there now in place, and cut the pipe with a fine-tooth hacksaw or use a cutter made for cutting plastic tubing.

Thanks for the link to the elbow!

The reason I was interested in replacing connection to the metal drain pipe is that after I disconnecting the form N fit from the sink drain, causing some movement of the pipes, I noticed water drip from the bottom of that metal nut. I was thinking perhaps a new slip joint (washer and nut) unless there is a better way to tie into that metal drain pipe would be a good idea while I was down there. What do you think?

 

[Reach4]

I noticed water drip from the bottom of that metal nut. I was thinking perhaps a new slip joint (washer and nut)

A new slip joint nut and washer would be a good idea. Click inbox, above.

 

[Jadnashua]

You may just need to crank the nut down a bit, but it helps if the tapered washer is in good shape.

 

[Plubit]

Would it be better to cut and glue PVC or ABS pipe than using various plastic slip joint elbows and extension tubes?

How far should one ensure the pipe rests inside the slip joint on the vertical metal drain pipe? Should the length be the radius length of the metal drain pipe so that it sits in the center of that vertical metal drain pipe?

Is a slip joint connection my only option for connecting to that metal drain pipe?

 

[Reach4]

Would it be better to cut and glue PVC or ABS pipe than using various plastic slip joint elbows and extension tubes?

Not in my opinion. The slip joint option is so much easier.

How far should one ensure the pipe rests inside the slip joint on the vertical metal drain pipe? Should the length be the radius length of the metal drain pipe so that it sits in the center of that vertical metal drain pipe?

No. The horizontal pipe should be past the washer, but not as far as the near edge of inside the vertical pipe. There is some good margin there. How about an inch past the washer as a number that gives good leeway either way.

Is a slip joint connection my only option for connecting to that metal drain pipe?

Those cast iron sanitary tees can crack, as unlikely as that seems. If you continue to get leakage, you may want to get that replaced with PVC. A plumber could probably do that in a few hours. My elapsed time for the two I did was measured with weeks on a calendar rather than a clock. I kept thinking I had already done the hard part, but the next step was always much harder than I anticipated.

 

[Plubit]

Those cast iron sanitary tees can crack, as unlikely as that seems. If you continue to get leakage, you may want to get that replaced with PVC. A plumber could probably do that in a few hours. My elapsed time for the two I did was measured with weeks on a calendar rather than a clock. I kept thinking I had already done the hard part, but the next step was always much harder than I anticipated.

I considered threaded female PVC, but on further research is seem metal male threads into PVC should be avoided. Is there a 1 1/2" threaded female to 1 1/2" threaded female galvanized steel coupler or union that would let me connect to the metal drain pipe and then connect using male threaded PVC?

Are you suggesting that attaching something like what I describe above to the tee on the vertical drain pipe would stress and possibly crack it?

I want to thank you again for your help. I really appreciate you taking the time to provide feedback!

 

[Reach4]

Are you suggesting that attaching something like what I describe above to the tee on the vertical drain pipe would stress and possibly crack it?

No, I was suggesting that it was possible that the cast iron sanitary tee may have already been cracked. So if you keep getting water coming out, it may not be the washer and nut, but water coming thru a crack.

I am not saying that is the case. Try the new gasket and new nut before widening the search for a different the cause of the leak.

Replacing a cast iron santee involves cutting pipes above and below the santee.

 

[Plubit]

No, I was suggesting that it was possible that the cast iron sanitary tee may have already been cracked. So if you keep getting water coming out, it may not be the washer and nut, but water coming thru a crack.

I am not saying that is the case. Try the new gasket and new nut before widening the search for a different the cause of the leak.

Replacing a cast iron santee involves cutting pipes above and below the santee.

Okay, I understand and appreciate the suggestion.

I think I'm going to try and keep the repair simple for now by replacing the zinc nut and washer on the metal drain and then direct the drain into the existing white plastic pipe using an elbow with dual sided slip joints as you suggested earlier. I would really love PVC coming out of the wall, but I'm thinking that's a little beyond my comfort / skill level at the moment.

Is the most correct way of getting PVC out of the wall in this situation to remove the metal waste connector from the tee and thread a short metal pipe into the metal tee and then use a fernco PVC flexible coupling to connect PVC to the metal pipe? Or thread a male PVC component into the metal tee? I'm guessing removal of the waste connector from the metal tee might require heat and some force, and that could result in a breakage that would then require additional work. Is that correct?

 

[Reach4]

Is the most correct way of getting PVC out of the wall in this situation to remove the metal waste connector from the tee and thread a short metal pipe into the metal tee and then use a fernco PVC flexible coupling to connect PVC to the metal pipe?

I am not sure what you are asking. I don't see the need for a Fernco coupling at this point. This is not to say that a coupling would not be useful if the threads on the existing trap adapter are messed up. In that case, then a right-sized adapter could work around that, but that adapter will probably not be on a local shelf.

You have a cast iron sanitary tee (santee) A with what I think is a galvanized trap adapter B. Unless you have to change that, I would keep that minus the nut. I would put a new nut C and washer on the trap adapter if tightening the existing nut a bit does not fix the leak. Or maybe just change the nut and gasket anyway. The new nut can be metal or plastic.

The white pipe D used for these "slip" connections is usually polypropylene. Let's just call it white pipe or white plastic.

The double offset tube, cut to size would be an alternative to using the slip elbow. It makes for more work, but gives one less joint.

 

[Jadnashua]

It looks like the fitting with the nut on it (a trap adapter) is leaded into the cast iron behind it. If you try to scratch the material between the adapter and the cast iron, is it relatively soft and turn shiny (lead?)? If so, if you want all of that to be plastic, you'd need to remove the lead from the bell of the housing. Then, you can get a Fernco donut seal that fits in for your 1-1/2" DVW pipe, stick that into the donut, and glue a pvc trap adapter to that, and the build out your tubular materials from there.

If you find that it is leaded in, you can use a drill bit to make it look like Swiss cheese, then grab the fitting with a big set of pliers, and pry it out of there. The holes give it some room to compress. Underneath the lead will likely be some oakum (oiled hemp rope). Once you get that out of there, you'd use a wire brush to clean up the bell of the cast iron so that the donut will fit in and seal. Note, while the DVW pipe's OD is standard, so that is easy for the donut, the ID of the cast iron bell is not, so they make the donuts in incremental sizes. It's sort of like Goldilocks...too small, doesn't seal; too tight, can't get the PVC pipe in; needs to be just right. So, once you measure it after cleaning, you might need to order a donut if you can't find one locally in the right size.