2013 Sundance with Atwood hot water heater. Have water pouring out of plastic drain plug. Second time this year. First time I changed the plug and no problem for 2 weeks. Woke up this morning and thought I heard a fan running.went outside and again water blasting through the drain plug, probably blew out 200 gallons of water overnight. Is this a failed pressure relief valve or something else? Any help appreciated. Thx
Water blasting out from hot water heater plug
- Thread starter gmb8585
- Start date
david-steph2018
Well-known member
When you installed the plug did it go in okay or get over tightened?
taskswap
Well-known member
If the plug went in all the way you might have a bad plug. Plastic shrinks as it cools and maybe the plug you bought was a wee bit under-sized out of the factory. This fitting is NPT (1/2" IIRC) which means it's a tapered plug and tapered fitting. You should start feeling resistance about 1/4 of the way in, and it should start getting very tight by halfway. The taper is crucial to how this type of fitting is meant to seal without an O-ring, which straight-thread fittings require. Try another source for a new plug. Some teflon tape can help too but if your plug goes all the way in, that won't fix it.
Spoke to Dometic customer service a few minutes ago. Told me there are 4 lines defense for a water heater and to replace all. The ECO-T stat which turns off heater when water reaches 145 degrees, then the Thermal cutoff at around 205 degrees, then pressure relief around 240 degrees. If all fail the plastic plug is last line of defense allowing water to blast through to relieve pressure and save tank from exploding. I'll look today at RV dealer and replace them all if available. Thx
jerryjay11
Well-known member
Interesting for sure. As a retired HVAC/R technician, I would think the pressure relief valve should have opened first. That would be the first thing I would change, but for safety sakes maybe it's not a bad to replace all 4 defenses.
david-steph2018
Well-known member
Thanks for the information.
I made an error in my last last post. After reviewing g the info on the parts I just bought the prv should go off at 205 degrees. I've decided to be cautious and turn hot water heater when I go sleep a d run a bit of cold into the tank and do the same when I leave the trailer for the day. BTW, those plastic plugs are a *****. Both times the head twisted off and I had to use a chisel as an easy out to remove the stem.
Dahillbilly
Well-known member
have a 2018 RV with same HW heater, remove the plastic plug every year to winterize system; never had a problem removing or installing the plug. Just make sure not to over tighten when installing it.
jerryjay11
Well-known member
I'll add, be sure to use only a hex (6 sided) head socket. The others tend to strip the plastic plug.
wdk450
Well-known member
In light of your conversation with Dometic, I would get the correct size metal plug as a short term fix, order the Dometic plastic part, when you receive the Dometic part remove the metal one (and keep it around as an emergency spare), get a round stiff wire brush for holes and clean out the tank threads, and install the Dometic correct part. If it still leaks, your tank threads are probably so messed up that they won't seal water properly. I don't think teflon tape is supposed to be used with plastic pipe plugs.
BTW, my Suburban 12 gallon water heater produced around 2007, has an original metal (brass?) pipe plug on it.
Having 2 systems of tank overpressure protection (pressure relief valve and plastic drain plug) seems like a little safety overprotection. In my my many years of RVing, I have NEVER heard of a hot water tank pressure exploding. Most everybody has had the overprotection valve leaking, (usually due to hard water deposits) though.
BTW, my Suburban 12 gallon water heater produced around 2007, has an original metal (brass?) pipe plug on it.
Having 2 systems of tank overpressure protection (pressure relief valve and plastic drain plug) seems like a little safety overprotection. In my my many years of RVing, I have NEVER heard of a hot water tank pressure exploding. Most everybody has had the overprotection valve leaking, (usually due to hard water deposits) though.
