OT-Tankless water heater frozen

Col. Forbin

Junior
Oct 2, 2012
1,367
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Any tips on thawing out a Rinnai tankless water heater? Cold water runs just fine, but no hot water is coming from the taps.
 

dawgstudent

Heisman
Apr 15, 2003
40,526
22,322
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Can't relate. I spend my extra $$ on TV's.

Is the water heater frozen or the hot water line from the water heater frozen?
 
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Aug 5, 2011
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I wonder if you could....

Any tips on thawing out a Rinnai tankless water heater? Cold water runs just fine, but no hot water is coming from the taps.

Pour Dale's on it and let it sit for a couple of hours** Seriously, if you have one of the propane tanks with a "Mr. Heater" type burner on it, I wonder if that would help thaw it out... Just a thought...But I'm not sure what would keep it from refreezing as cold as it's been for a long period of time....Is there any way to insulate it?
 

Col. Forbin

Junior
Oct 2, 2012
1,367
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Right now I got a hair dryer in the water heater mount outside. Gonna see if that helps. I’m assuming it’s frozen at the water heater, not positive though.
 
Sep 21, 2017
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Any tips on thawing out a Rinnai tankless water heater? Cold water runs just fine, but no hot water is coming from the taps.


Is your WH mounted or accessed on the exterior of your house? When you say no hot water do you mean there is no water at all or just cold water but it is running? I imagine your hot waterlines are frozen at the outlet from the WH.
 

Col. Forbin

Junior
Oct 2, 2012
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It is on the exterior. And there is zero water at all coming out of the hot water faucets. My cold water faucets are working just fine.
 

dawg0204

Redshirt
Dec 13, 2020
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I’ve had this happen before. It’s your copper pipes. A hair dryer works but takes forever to thaw it. Boil some water and pour it on just the pipes (not the system itself) and it’ll thaw out quicker. May have to do it a few times but it works.

If you can get a heat lamp and rig it up to where it shines on the pipes, it will keep the lines from freezing. Lowe’s or Home Depot would carry it, although good luck trying to find one now.
 

pmack3641

Junior
Aug 9, 2019
509
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Its possible the cold water line into the heater is frozen. The hot line coming out of the heater wouldn't freeze. Second possibility is the heater itself is frozen or stopped working for another reason. Your cold water faucets are separate from the HWH so my guess is the cold line going in is where your issue may be.
 
Sep 21, 2017
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I’ve had this happen before. It’s your copper pipes. A hair dryer works but takes forever to thaw it. Boil some water and pour it on just the pipes (not the system itself) and it’ll thaw out quicker. May have to do it a few times but it works.

If you can get a heat lamp and rig it up to where it shines on the pipes, it will keep the lines from freezing. Lowe’s or Home Depot would carry it, although good luck trying to find one now.


This is correct. Tun on a hot water tap in the house when you start to thaw the pipes. This will get the water running and clear up any blockages faster once you thaw the line.
 

garddog

Sophomore
Dec 10, 2008
793
100
43
The better question is who allowed for a tank less system to be installed outside. They aren't designed for that. To stop in future you will have to leave a faucet dripping just like folks do on cold lines.
 

Col. Forbin

Junior
Oct 2, 2012
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Just about every new construction house that i have seen with a tankless has the same set up as I do.
 

garddog

Sophomore
Dec 10, 2008
793
100
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Builders love doing things the cheap way. No water lines or water heaters should ever be put "outside" where the temp is not regulated.
 

TrueMaroonGrind

All-Conference
Jan 6, 2017
4,129
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Just about every new construction house that i have seen with a tankless has the same set up as I do.

IDK where you live, but I don’t see how that is code compliant. Up here they would freeze a few times a year if they were mounted outside. Ours is in the attic. Most others I know of are either in the attic, garage or laundry room. Never heard of a hot water heater mounted outside.
 

msugolf

Junior
Dec 29, 2008
834
393
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Any tips on thawing out a Rinnai tankless water heater? Cold water runs just fine, but no hot water is coming from the taps.

Actually had this same issue this morning with a Rinnai no less. Turn sink hot water lever to on and go outside with a hair dryer and warm up all the pipes going in to the water heater. Might take about 5-10 minutes but it should start to run. Leave it dripping at the faucet for the rest of the day.
 

johnson86-1

All-American
Aug 22, 2012
15,177
5,721
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The better question is who allowed for a tank less system to be installed outside. They aren't designed for that. To stop in future you will have to leave a faucet dripping just like folks do on cold lines.

I don't think it's uncommon to have tankless systems on the outside wall. The only people I know of that have them have them on the outside. Presumably a lot of people have them and I don't know about them because they are in the attic or somewhere else not exposed. Have to have the feed well insulated and even then need to keep some water moving.
 

Russ Wheeler

Redshirt
Aug 3, 2020
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My tankless heaters are in the attic. No way they should be outside.

But to make you feel better, one of the cold water faucets in my bathroom isn't working. I'm guessing it's frozen through an exterior faucet.

But yeah, I'd guess youre cold water line going to the tank is what's frozen.
 
Sep 21, 2017
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Just about every new construction house that i have seen with a tankless has the same set up as I do.


I believe it has to do with the ventilation requirements. A coworker just installed an interior tankless himself and he said he was caught off guard. He had to do some surgery on his roof to get a large enough vent pipe installed.
 
Nov 16, 2005
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Had a bathroom cold water faucet frozen yesterday. Propped up a hair dryer blowing up under the cabinet for about 15 minutes and had the hot water running and it thawed out.
 

Dawgology

Redshirt
Sep 15, 2011
828
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Putting tankless water heaters on the outside of your home in MS is pretty standard. About 90% or more are done that way in Mississippi. You or your plumbers should have insulated those pipes at install. Just like you would an outside faucet. It rarely gets below freezing for extended periods of time and actually reduces the damage that can be done to a home if a water leak occurs at the tank (which is much more common in Mississippi than consecutive days of temp not rising above freezing).

Since it’s Rinnai I’m assuming it’s gas. When you turn on your hot water do you hear your gas elements kick on? Your supply pipes should have been heat traced and insulated when installed. Rinnai’s are guaranteed not to freeze down to 0 degrees on the exterior tankless systems when installed properly. You need to have a certified professional take a look and then jerk a not in your plumbers *** if he didn’t install it correctly.
 

horshack.sixpack

All-American
Oct 30, 2012
12,136
9,475
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I see most new construction in the Jackson area with them stuck on the outside wall. It certainly avoids needing to add a vent. Hopefully the cabinet always stay in place even if the guts die. It would suck to have to do masonry work to replace a dead one years down the road.
 
Sep 26, 2012
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Is your attic an insulated space with the spray on foam on the decking? If not your uninsulated space in your attic is subject to roughly the same temps outside, right? What would be difference? I have seen both types of installations, outside like Col.'s and in uninsulated attics......
 

Russ Wheeler

Redshirt
Aug 3, 2020
2,430
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Had a bathroom cold water faucet frozen yesterday. Propped up a hair dryer blowing up under the cabinet for about 15 minutes and had the hot water running and it thawed out.
Yep set a space heater up and it thawed after about an hour, just now. Going to leave that bad boy dripping now. Thought I could get away with it last night but lesson learned. Talk about being in a better mood.
 

Dawgology

Redshirt
Sep 15, 2011
828
1
0
Quick question: did you lose power for an extended time?

If you lost power for an extended amount of time and didn’t drain the water out of the unit you could have busted your heat exchange if you were without power long enough for it to freeze. Hopefully you didn’t lose power and that’s not what it is.
 
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Motodawg

Senior
Apr 19, 2018
607
578
93
I posted a reply but I don’t see it, so I’ll try again. Keep water moving. I can’t tell you how to thaw the lines out safely but I can tell you that the heater maintains it’s temperature internally. As long as you have power, it is safe. I’m a plumber of 13 years so you can trust what I’m saying. I don’t want my post to be seen as soliciting business so I won’t leave my number. My company is Top-Notch Plumbing Service in Brandon. Best wishes my friend. Hail state and GTHOM
 

Jeffreauxdawg

All-American
Dec 15, 2017
8,891
8,003
113
Putting tankless water heaters on the outside of your home in MS is pretty standard. About 90% or more are done that way in Mississippi. You or your plumbers should have insulated those pipes at install. Just like you would an outside faucet. It rarely gets below freezing for extended periods of time and actually reduces the damage that can be done to a home if a water leak occurs at the tank (which is much more common in Mississippi than consecutive days of temp not rising above freezing).

Since it’s Rinnai I’m assuming it’s gas. When you turn on your hot water do you hear your gas elements kick on? Your supply pipes should have been heat traced and insulated when installed. Rinnai’s are guaranteed not to freeze down to 0 degrees on the exterior tankless systems when installed properly. You need to have a certified professional take a look and then jerk a not in your plumbers *** if he didn’t install it correctly.

I always wondered if there was any other reason than to prevent running stacks through the roof? It makes sense on a retrofit in the deep south I guess, but new build... That's a hell of a way to cut a little cost.

How it should be done everywhere.

View attachment 19497
 

Hugh's Burner Phone

All-American
Aug 3, 2017
5,416
6,358
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I had mine freeze several years ago. Ever since when it gets cold I leave the hot water dripping. Not enough to trip the heater into coming on, but enough to keep a current going to keep it from freezing.
 

dawg0204

Redshirt
Dec 13, 2020
25
0
1
Yeah, looks like yours is completely covered. Mine has the copper pipes outside of the box. Might not want to pour boiling water on your box lol

I would think that box would have some freeze prevention capability in it?
 

dawg0204

Redshirt
Dec 13, 2020
25
0
1
This too. Keeping water moving is key. My heat lamp busted in the middle of this and I just let the water run and it hasn’t frozen up yet.
 

dawg0204

Redshirt
Dec 13, 2020
25
0
1
Agreed. I don’t know why this isn’t standard, must be due to cheapness. That’s all I can think of why my dryer vent goes into my garage - just a dumb design/oversight.
 

patdog

Heisman
May 28, 2007
60,477
31,695
113
Yeah. I'm just floored that people are putting those things on an outside wall. I wouldn't do one as a retrofit to begin with because it's so much cheaper and easier to just replace like for like, which is exactly what I did a year or two ago, went electric cause that's what I had.
 
Dec 9, 2018
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I posted a reply but I don’t see it, so I’ll try again. Keep water moving. I can’t tell you how to thaw the lines out safely but I can tell you that the heater maintains it’s temperature internally. As long as you have power, it is safe. I’m a plumber of 13 years so you can trust what I’m saying. I don’t want my post to be seen as soliciting business so I won’t leave my number. My company is Top-Notch Plumbing Service in Brandon. Best wishes my friend. Hail state and GTHOM
That's what I thought and how it was described to me when I built my house. I have one on an outside wall because that is how it was designed. 11 degrees last night. I didn't drip or run any water through it. No issues.
 
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