On Demand Hot Water and gas lines

[Cheese]

Remodeling our 1999 Airsteam Bambi, needed tools to redo PEX lines.  I bought the copper clamping breaker, new clamping rings, clamping tool and short lengths of red and white pipe.  All new to me, been soldering copper for 50 years, including my house done 35+ years ago.

FWIW...I use a combination of copper and PEX. Copper for the long runs and PEX where you have a bunch of short connections like on a bathroom shower/diverter valve.

The PEX is also nice for large radius situations. For one application on an in-wall toilet, I built a wooden jig with the radius I needed and then heated the PEX with a heat gun and placed it in the fixture to cool down. About 2-3 hours later I removed the PEX and it was formed exactly like I needed it to be, it was a cold water run...don't know what would happen if it was on a hot water run.  [tongue]

 

[rst]

My house hot water heater, AO Smith is 21 years old and I originally plumbed with 3/4" copper every where.  I intend to replace with an on-demand and rerun the hot water feeds with 1/2" PEX as currently it takes forever for the hot to arrive at kitchen our sink despite only being 20 some feet away.

 

[Cheese]

I intend to replace with an on-demand and rerun the hot water feeds with 1/2" PEX as currently it takes forever for the hot to arrive at kitchen our sink despite only being 20 some feet away.

I installed a Rinnai on-demand and it's absolutely been one of the best moves I've made for the house. You'll be tickled with the performance once you install a tankless water heater. I'd do it again in a heart beat. I did a 3/4" copper line in & a 3/4" copper main out with branches off of that.

 

[Ron B]

I installed a Rinnai on-demand and it's absolutely been one of the best moves I've made for the house.

I have an A.O. Smith that is going on 31 years.  I thought about a Rinnai, but how much gas do these suck?  Is it noisy?  I am afraid my meter may be too small and if my furnace and the Rinnai kicked on, I was afraid I may not have enough gas volume.  (Furnace is also 31 years old-an Amana back when they made good ones-it has a s.s. heat exchanger)

 

[Cheese]

I thought about a Rinnai, but how much gas do these suck?  Is it noisy?  I am afraid my meter may be too small and if my furnace and the Rinnai kicked on, I was afraid I may not have enough gas volume. 

[member=72457]Yardbird[/member]
Any of the larger tankless heaters that will supply 2 or more fixtures at the same time will need a 3/4" gas line and a 3/4" water line. Another option is to have the gas pressure increased on the 1/2" line, that will work & is recommended as an alternative.

The Rinnai is not noisy at all, the only time you can hear it is if you go downstairs and stand right next to it. Even then the relay makes a soft click, the red "in use" light comes on and you hear a slight hum. The hum is so slight that at first you don't really know where it's coming from. It is not at all like a gas furnace that sounds like an after-burner. You can also dial in your water temperature in 1º increments.  [cool]

 

[Holzhacker]

Have to chime in with Cheese here. You'll need at least a 3/4" gas line off of your main run coming from your meter. You can't just replace a few feet of the 1/2" with 3/4". The unit will under fire and not heat properly. When I was a Plumbers apprentice we would have to go back regularly to redo the gas lines for people. They would hire the lowball contractor who didn't know, didn't upsize the gas line and the unit wouldn't work right. They would call use, we'd replace the gas line and it would work fine. Of course sometimes the water lines and direct vent pipe had to be redone as well.
Tankless units are great. Nice and quiet. Good hot water. If you can do the install yourself its worthwhile. If you have to pay someone not so much. Around here an install runs +/-$4500.
I always tell people if your house is party central for the holidays or you have teenage girls the tankless is the way to go. Otherwise based on cost go with a 75 gallon and you'll be fine.
In your case I would recommend running some amount of 3/4" copper off of the unit to your 1/2" pex. We don't use pex around here so I don't know about temp limitations.

 

[mino]

I would second the on-demand gas heaters full on.

We had it in our flat where I grew up, was 20kW I believe and while it was noisy (70's tech) it had one thing going that I sorely missed since moving out:

Hot water at the temperature I want and when I want. Including 40C just-warm water for bath (without any risks of bacteria contamination of the water) or 70C "burner". Oh how I miss that!

- with central heating (current flat) the temperature fluctuates 55-60 and I cannot really tune it down - it must be kept above 55C when circulating the tubes for sanitary reasons. So you kinda burn yourself every time you forget to mix it.

- with local tank-based heaters (had both electric dedicated and central heater with tank for water), the heater generally cannot keep up once the tank is empty and when it can the temperature suddenly changes - a PITA. And the efficiency savings are anyway eaten up by the heat losses of the tank so is a wash.

The only other (good/comfortable) option that compared to tankless gas heater for me was at a friend who has a huge 3000-liter heat-accumulator tank heated from solar just below the bathroom/kitchen with a very short circuit from it for hot water with auto regularing valves. But he built a house around this setup, essentially...

 

[Bob D.]

"You'll need at least a 3/4" gas line off of your main run coming from your meter. You can't just replace a few feet of the 1/2" with 3/4"."

You can't just throw a pipe size out there for a gas appliance and call it good. The size needs to be calculated based on where this appliance/equipment is tapped into the system, what else is on the system, number of fittings, length of pipe runs, etc. Look up the Mechanical Code for your area, don't guess.

 

[mino]

"You'll need at least a 3/4" gas line off of your main run coming from your meter. You can't just replace a few feet of the 1/2" with 3/4"."

You can't just throw a pipe size out there for a gas appliance and call it good. The size needs to be calculated based on where this appliance/equipment is tapped into the system, what else is on the system, number of fittings, length of pipe runs, etc. Look up the Mechanical Code for your area, don't guess.

Not enough. Call a certified gas installer. And double-check his calculations/proposals.

Really folks, you should NOT mess with this stuff. Even if the law allows it at your place. Electricity is "fun to play with" compared to your home turning into a fireball one day. Gas is very safe when done properly but can be a family killer when done the "it will be fine" way.

Over here it is even illegal for a non-certified installer to touch the gas pipes. One cannot even lay them in prep like you mostly can with electricity. And for a good reason.

 

[Coen]

Really? 95% of CO deaths in this country is with installations that were recently serviced or installed by a certified installer

 

[Coen]

My house hot water heater, AO Smith is 21 years old and I originally plumbed with 3/4" copper every where.  I intend to replace with an on-demand and rerun the hot water feeds with 1/2" PEX as currently it takes forever for the hot to arrive at kitchen our sink despite only being 20 some feet away.

You should check what part of the time is due to flow time and is due to start-up time.

For long distances and small amounts of hot tap water, get an electric boiler in the kitchen or a combi Quooker.

 

[mino]

Really? 95% of CO deaths in this country is with installations that were recently serviced or installed by a certified installer

And it is as expected. Most issues happen when something changes - when nothing is being done, nothing is broken.

There is exactly zero way someone who is not sure if 1/2 or 3/4 tubing is needed has more knowledge and experience in gas installs to override professional training and experience. Zero.

Personally I have studied Physical Chemistry and Electrical Engineering to the point I can make a gaseous fluids simulation of that heater's fire zone. STILL, I would not go messing with the gas lines thinking "how smart I am and how stupid people with 1/100 the understading of the thing are".

Truth is, they may be stupid, very stupid, BUT they do know the important things as they tend to know which are the important things while I have none of the specific experience nor training in this install field.

 

[Packard]

My first apartment (1971) had a gas stove.  But the pilot light kept going out so I had the service man turn that off and I lit the stove and the oven with a match.  Not very convenient, but at least the apartment would not fill with gas. 

The landlord would not replace the stove. 

I have never felt confident having a gas stove in the house.  So when it came time for a new cook top, I went with induction.

I would like on-demand water heat, but we don't have gas piped in where I live and the other option is electric, which tends to get expensive. 

Are there oil-fired on-demand water heaters?

 

[Coen]

Really? 95% of CO deaths in this country is with installations that were recently serviced or installed by a certified installer

And it is as expected. Most issues happen when something changes - when nothing is being done, nothing is broken.

Well no, especially because the # of CO deaths was used as an excuse to ban non-certified persons from installing gas burning central heaters. While the law, even people abide by it... would only affect the 5% of the total...

 

[Bob D.]

"Not enough. Call a certified gas installer. And double-check his calculations/proposals."

That was my point, but I did not tell others they should call a licensed contractor. I merely
pointed out that it is more involved than upsizing by the seat-of-your-pants method. I
figured no one needed a dressing down like you gave them. I just made them aware of some
of what's involved in calculating the correct size which may not have been known to them.

 

[Coen]

Remodeling our 1999 Airsteam Bambi, needed tools to redo PEX lines.  I bought the copper clamping breaker, new clamping rings, clamping tool and short lengths of red and white pipe.  All new to me, been soldering copper for 50 years, including my house done 35+ years ago.

FWIW...I use a combination of copper and PEX. Copper for the long runs and PEX where you have a bunch of short connections like on a bathroom shower/diverter valve.

The PEX is also nice for large radius situations. For one application on an in-wall toilet, I built a wooden jig with the radius I needed and then heated the PEX with a heat gun and placed it in the fixture to cool down. About 2-3 hours later I removed the PEX and it was formed exactly like I needed it to be, it was a cold water run...don't know what would happen if it was on a hot water run.  [tongue]

You can just bend pex cold using a spring, just like PVC electrical piping.

 

[Ron B]

I thought about a Rinnai, but how much gas do these suck?  Is it noisy?  I am afraid my meter may be too small and if my furnace and the Rinnai kicked on, I was afraid I may not have enough gas volume. 

[member=72457]Yardbird[/member]

The Rinnai is not noisy at all, the only time you can hear it is if you go downstairs and stand right next to it.

Thanks Cheese.  The reason I asked is I bought a Rinnai to install fifteen years ago, but got deathly sick and never installed it.  Bad reaction to a Rx drug and ended up with brain fungal flu and it took me quite a while to bounce back.  I am (finally) planning the remodel now and thought about installing it but was concerned about the noise since it would be in the laundry room.  I already have the gas lines resized, but saw my model (2532FFU-N) draws between 15,000 and 185,000 BTUs.  My meter is only 175 CFH and also feed a furnace and another water heater, so that meter is too small.  I just thought something sucking 185,000 BTUs would be like having a jet engine installed on your wall and was shying away from it for that reason.  I will have to rethink this.

 

[Cheese]

Thanks Cheese.  The reason I asked is I bought a Rinnai to install fifteen years ago, but got deathly sick and never installed it.  Bad reaction to a Rx drug and ended up with brain fungal flu and it took me quite a while to bounce back.  I am (finally) planning the remodel now and thought about installing it but was concerned about the noise since it would be in the laundry room.  I already have the gas lines resized, but saw my model (2532FFU-N) draws between 15,000 and 185,000 BTUs.  My meter is only 175 CFH and also feed a furnace and another water heater, so that meter is too small.  I just thought something sucking 185,000 BTUs would be like having a jet engine installed on your wall and was shying away from it for that reason.  I will have to rethink this.

I installed the RC80HPI model about 12 years ago, it's rated at 157,000 BTU and it really is as quiet as a mouse. I'd highly recommend the install especially as you've already purchased the item and you've installed larger gas lines. After that it's really a cake walk, just use a ton of common sense and then double & triple checking connections goes a long way. Just purchase the tools/consumables that you need and go forth. It isn't difficult it's just check & double check, let common sense and introspection be your guide. I went through a bunch of soap water but just mop it up and be grateful that the connection is leak free.

Just to let you know that installs like this are possible under difficult conditions, my install was done while the existing Ruud water heater was leaking on the floor and my wife fully expected to continue to wash clothes and dishes in the blissful manner that she always has, creativity in house repair is a God send.  [big grin]

Again...one of the best home improvements moves I've made.

PS. Sorry to hear about the health issues, that's a real bummer, good to hear you're now good to go.  [big grin] [big grin]

PPS. Thanks to Seth for breaking up this thread and pointing it in the proper direction. This stuff is important for future archiving and searching ease. If you can't find it...what's it worth?

 

[Ron B]

Cheese:
Thanks for the response.  I resized my other pipelines then did a check on for leaks by tapping a schrader air valve into the end of an black iron cap, then put 100 PSI to it.  I checked 24 hours later and it was still at 95 PSI, and I figured it could drop that much just due to change in air temperature dropping. I figured if it did not leak at 100, it is not going to leak at 5.
  The drug I was taking was for a FDA approval testing to get it approved for severe psoriasis. The drug suppresses parts of your immune system.  After my reaction I was dropped by the study as their drug Guinea pig.  Later I found out 48 of 238 people taking this test died from this same brain fungal flu that I had, and I had three different bouts with this flu.  Since things were fuzzy in my mind, i thought it best to just stop, so I finished it on the outside but left the inside as a shell and walked away.  Time for me to restart and just trying to see if the Rinnai was still an option.

 

[Cheese]

I keep a bottle of this stuff around for testing leaks as that's what it was specifically designed for and it's non-corrosive, just used it the other day to check fittings on an air compressor. There's an applicator/dauber in the cap.
https://www.homedepot.com/p/Oatey-8-oz-All-Purpose-Leak-Detector-302092/100151681

[attachimg=1]

Also on some very stubborn water pipe connections, PTFE tape sometimes just doesn't work even after several re-tapes, so I keep this stuff around. It's approved for potable water and gas lines and is popular in avionics.
https://www.homedepot.com/p/RectorSeal-4-oz-No-5-Pipe-Thread-Sealant-25631/100351066

[attachimg=2]

Finally it may be code in some locales to use yellow PTFE tape for gas lines, that's what I use as it's 2x-3x thicker than the white version.
https://www.homedepot.com/p/Oatey-1...Vp8LCBB243Q9gEAQYASABEgKWZvD_BwE&gclsrc=aw.ds