Don’t Use Permatex®!
WARNING! Permatex® is not a suitable pipe dope! It is especially not suitable pipe dope for potable water! This is so critically important, let me repeat it:
Permatex® is not a suitable pipe dope for potable water! It’s toxic!
Okay. Now that I have that out of my system, let me explain:
Permatex® is a gasket sealant designed for use on engine gaskets. There are two types: Type A which is “hardening”, and Type B which remains pliable. Both types are made of highly toxic chemicals designed to withstand the heat and pressure and contact with engine oil and engine oil additives. It was never designed to be a thread sealant of any kind, never mind household water supplies.
Why am I carping on this? Because I just returned from a job where someone had used Permatex® Type A as a pipe dope on the main water line running into a mobile home. Obviously, the pipes would not come apart the way they’re supposed to. So, I applied heat from a torch. And what did I smell? The distinctive odor of Permatex® gasket sealant.
I suppose the former owner of the mobile home thought he was being clever in getting troublesome galvanized pipe to seal by using it. In reality what he was doing was A) poisoning his family and B) making it impossible to re-plumb without taking that connection completely out of the system. Permatex® Type A does not come back apart once it hardens! I ended up destroying the pipe trying to get it apart. (Hey, I figured I had nothing to lose by trying.)
Anyway, in addition to “Teflon tape” there are two pipe joint compounds suitable for potable water supplies: One is TFE paste, available usually under the hardware store’s label. The other is called Rectorseal®. The latter is better for sealing troublesome pipes that are going to be under high pressure, and for gas applications. (In fact, in some jurisdictions, you have to use Rectorseal® or “yellow dope” on gas lines. Regular TFE paste is not “code”, so check with your local building department before choosing a dope for gas lines.)
For regular water lines TFE tape or paste works just fine. And if you have some old threads that you expect you’re going to have trouble getting to seal, “double dope” them. First, wrap the threads with your tape (one or two wraps, depending on how bad the threads are), then smear a good even coat of TFE paste over that. If the threads are good enough to pull up tight, that puppy will seal!
So, no more Permatex® on the potable water pipes, okay?
Okay!
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