Heater - Stripped exchanger drain plug

carlos31820 · Apr 7, 2013

I have a Jandy Legacy 250 natural gas heater. On the left side of the heater, there is a polymer/plastic threaded drain plug (part 43 in the diagram below). I have partially stripped this drain plug and now water squirts out whenever the pump is running. I have it holding right now by using some teflon tape. I'm about to order a replacement plug hoping its the plug itself and not the polymer housing on the heat exchanger. If a new plug doesnt do the trick, is there a way to fix this short of glueing the plug permanently in? I live in Georgia and dont close the pool for winter so I dont really have a need to drain the exchanger.

JasonLion · Apr 7, 2013

Getting the correct thread tap and carefully rethreading the hole often works. Doing this might also make things even worse, but you don't have much to lose at this point.

CUTiger78 · Apr 8, 2013

I've got a Teledyne Laars 175K BTU NG unit with brass drain plugs. A couple of years ago, the pool closing company managed to strip the threads in the plug hole. My temporary solution was a cork. Bought a bag full in various sizes and crammed in the one that fit best. Worked so well (no leaks!) that I haven't actually repaired it yet.

I realize that's shade tree mechanicing at best, but....

Good luck!

gtemkin · Apr 8, 2013

It appears from the shopping site picture that the plug uses straight threads with an o-ring seal. The sealing is meant to be accomplished by the o-ring only, so as long as your threads can compress the o-ring well enough, you should be OK. If what really happened is you cross threaded the plug, and the o-ring isn't being compressed evenly, because the plug is tilted, then re-threading the header so the thread is straight would be a good approach. If the threads are so bad that there's very little plastic left to thread, then you could install a Helicoill or other brand threaded repair insert.

Another, possibly simpler way is to use a test plug. These are sort of universal fit devices with expanding rubber bushings. Check out what Mcmaster-Carr has. I'd choose something that had a temperature range up to 250F.

http://www.mcmaster.com/#expansion-test-plugs/=m8iirk

carlos31820 · Apr 8, 2013

Right now it's been holding for two days by just putting teflon tape on the plug. Your test plug idea is genius, however. I was ready to epoxy that sucker in there for good. We don't close the pool here in west central Georgia.

carlos31820 · Apr 11, 2013

gtemkin said:
Another, possibly simpler way is to use a test plug. These are sort of universal fit devices with expanding rubber bushings. Check out what Mcmaster-Carr has. I'd choose something that had a temperature range up to 250F.

http://www.mcmaster.com/#expansion-test-plugs/=m8iirk

Im posting an update for anyone else who may have this problem. I also want to give credit to gtemkin for his brilliant suggestion to try a test plug.

I ordered mcmaster part number 9191T33. It's a half inch 302 stainless steel plug rated to 250 degrees.

It works perfectly. Photos below showing the test plug next to the original teflon-tape covered plug and an additional photo showing the test plug inserted in the heater.

gtemkin · Apr 11, 2013

Glad it worked and you were able to find something that fit so well. I have an english car hobby, which demands an open mind to stopping leaks of oil, coolant, brake fluid and smoke (from wires

).

Only caution I have is that the toggle clamp force not be too much because then you'd be putting a severe outward force on the plastic; but that's something you can judge fairly well when you clamp it and as long as you're not having to hit the lever with a hammer you're likely just fine for the long term.