I'm trying to replace the water supply turn valve under my bathroom sink. Whoever installed it put a yellow cement (plumbers cement?) on the threads between the nuts and the body of the valve. Is there a solvent that will dissolve the cement? All I can tell you about the cement is that it's yellowish in color. Here's a picture of the type of valve I have.
if the reason ur changing the valve is because it's not working, then don't change it, replace the stem only, behind handle loosen nut, turn stem counter clockwise till it comes out, do same w/new valve, put new stem in old valve, just make sure you remove any remains of old washer. I do this all the time, it's saves time and a lot of trouble and the outcome is the same. As far as cement goes, it maybe rectorseal #5 oilbase pipe thread compound since the valve you showed has compression connections on in and out sides.
Yes, it is a type of pipe dope (thread sealer). There are joint and gasket sealers sold world-wide. Hercules, Tap-con, Dope Pro and etc. all have sold this type of product. The older ones ALWAYS dried to a cement like seal. There is no solvent available for this issue. Unfortunately, if an old version was used, you only have 2 options available. 1. You can use your torch to heat and loosen the product form the valve. The real problem here is that if you are using the type of valve you posted in the picture, you run the great risk of permanently ruining the valve anyway. 2. Simply cut behind the valve and solder in a new one. Use the tape thread sealer and off you go. This is BY FAR the best option. Write to me if you have any questions. I'll be happy to help anytime. EDIT: Bill, Here's the issue. The pipe dope usually remains somewhat flexible for a long time. However, penetrating oil will not do the job. If you have a Monkey wrench, vice grip or a slip wrench (aka Channel) you have a good chance. You can heat the joint with a hair dryer. This may soften it enough. Hold the valve firm, with one of the above in one hand, and loosen the nut with the other. Vice grips work best to hold the valve steady. There are other options if this fails to work for you. One is to cut the feed line, and splice a new one on (using compresion fittings or a pipe splice). The best option is to turn the water off to the valve, cut the pipe below/behind it, and solder a new one on. If you are worried about soldering, buy a tool and die thread maker (inexpensive), create new thread and screw a new valve into place. If you are inexperienced at this, the soldering option is best. Vote for me, and feel free to write again should you have any questions. The return mail option did not work.
