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Ask Dave: Should I use tape on plastic water heater drain plug?

Dear Dave,
My water heater has a plastic drain plug. Should I use Teflon tape on the threads? Also, how long is too long to leave water in the tank between trips? We go on about 6-9 trips a year. Thanks! —Pete

Dear Pete,
It seems to be water heater week around here! If you have a plastic drain plug, then it should be an Atwood model. I would first verify that it is. If not, it would be a Suburban and need a metal plug with an anode rod. I have come across units where a previous owner did not maintain the unit and did nothing to the Suburban water heater and let hard water sit until the anode rod was completely gone. Then when someone did pull the plug, it looked as if there was just a drain plug and they replaced it with a plastic plug not knowing better. Yikes.

Using tape on a plastic water heater drain plug

I have never used pipe tape on the plastic drain plug for an Atwood water heater as the numerous manuals I have read and the RVIA certified training program simply state to “reinstall the drain plug and pressure relief valve” in the sections regarding winterizing, flushing, and de-winterizing.

That being said, I was told by a certified/licensed plumber that the pipe or plumbers tape is not a sealant, but rather a lubricant for hard metal to allow a tighter connection. At Winnebago we installed them with no tape and did a water test before blowing out the system and shipping them. I have seen tape on used units; however, I would assume it was either due to a leak or not knowing what the recommendation was.

Here is a unit we worked on for videos that had two plastic drain plugs. Notice how corroded the threads are on the drain! I would recommend a wire brush like the kind we use to clean battery cables.

There are several people that would state that “a little tape doesn’t hurt.” But I would caution against the use of tape on your plastic water heater drain plug. There may be too much of a buildup on those fine threads that could lead to cross-threading. I guess the whole idea is to keep it from leaking and make it easy to remove when it needs to be drained.

Use an Atwood water heater drain plug

One last tip: I always replace the plug with an Atwood plug. They are threaded properly and not tapered like some on the aftermarket. You can get one on Amazon here.

How long you can leave water in your tank

As for how long to leave water in the tank, it depends on the quality of water you are using. Since most of the water comes from a campground source, it will be hard water and will have minerals, lime, and calcium. This water tends to get “skunky” fairly quickly, so I typically drain the water after each trip unless I am going out fairly soon. Hopefully, we can get some feedback from other readers in the comments here.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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Bob Weinfurt
4 months ago

What I did to simplify the draining process on my old motorhomes water heater was use a car radiator petcock instead of the plug. I leave it open over the winter and come spring just finger snug it closed. My heater is just propane fueled with no anode rod.

Last edited 4 months ago by Bob Weinfurt
Bob
4 months ago

The problem about the corrosion on the threads of the water heater is easily solved. After cleaning the threads, or before they get bad, put some plumbers grease on them. It stops the rust and corrosion and makes it easier to remove and reinstall the plug or anode rod. I recoat mine every time the anode rod is removed.

KBowden
4 months ago

I have the Atwood system, and the plug tends to drip even when it feels tight. I tighten it further to stop the drip but afraid of breaking the plastic plug as I do so. So far I haven’t, but I think I’ll order a couple of those plugs as backup. I considered the tape, but was concerned with the temperature of the unit.

Is there a recommended torque on this plug, not to exceed type?

Steve
4 months ago
Reply to  KBowden

Teflon tape is very high temp tolerant. The plastic plug will melt well before the tape.

Bob p
4 months ago

I have always used Teflon tape even on plastics, but I only wrap a turn and a half. You are correct it’s not a sealant but a lubricant to allow the fitting to tighten better. The area people get into trouble is wrapping the tape in the wrong direction. It has to be wrapped so the tape doesn’t unwrap as the threads are tightening. Being right handed I hold the tape in my left hand, the fitting in the right hand and roll the fitting “away” from me. This is the same direction the fitting will be turned screwing into the place it’s going. Going the opposite direction will cause the tape to unwrap from the threads and will serve no purpose other than looking bad. Over 50 years doing it this way and haven’t had a leaker yet.

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