Looking for feedback from the all-knowing OB.

Currently have a single propane water heater in the garage of a 1 story home in North Texas. Family of 5, normal usage with 2 bathrooms.

My home is 20 years old, and has the original water heater (I suspect, will confirm tomorrow). No known issues presently.

Would converting to a tankless propane water heater help save us on propane costs? Most people that have them say they love them. I believe they are more efficient, and not wasting energy keeping water hot all the time.

- Is switching the unit out worth it, or should it only be considered if my current tank totally craps out?

- Assume that I could get the tankless unit at a pretty deep discount, and would only pay for install- does this make looking at converting worth it?

- What size units should I be looking at?

I appreciate all opinions. Thanks!

True but set the temp at max and adjust the knob at the showers. I can't remember the size of the heater but it was enough for two showers.

If you really put pencil to paper, it'll take a long time to pay for the extra cost in propane alone. The install is the kicker and there will be a lot of factors that determine how much it'll cost. Someone already mentioned gas line size (although Navien has a model with a 'pump' on the gas inlet that can pull 200K btu/hr through a 1/2" line). Venting is another big cost for some of them.

If you're serious, look at certified installers for Navien. I'm a former plumber that built my own house, and I went with Navien. 6 years trouble free so far. Rinnai is awesome too, but back then they had higher installation costs, especially on retro-fits. Maybe they've changed, but they used to have a proprietary vent system that was astronomical.

I just got back from Pagosa/Wolf Creek and thought of you, COJ! Beautiful up there!

We have a navian tankless on propane that has overall been great, even for showers on the opposite side of the house there is hot water in less than a minute. Ours is on the exterior of the house and we have had some freeze issues due to lines that weren't insulated in the attic freezing up. We had a small leak after snowpocalipse that was a $15 part replacement. I may have solved the pipe issue by putting a wire pipe heater on the lines in the attic with the pipe insulation on top.

1Aggie99 said:

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We made this move a couple of years ago. Tankless is nice and 99% of the time it works fine. One thing I forgot to factor in was our old heater would still pump hot water even when power went out. We have gas tankless but everything operates on an electric control panel.

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This is a really good point. Unless you have back up power, you lose hot water when the power goes out. A simple old school tank heater keeps working. Tankless heaters are prone to freeze and bust too with no power. They have little electric heaters that will kick on to prevent that.

We moved to tankless for two main reasons. 1. Unlimited hot water (teenagers). 2. Not having 80 gallons of water in the attic sitting there waiting for the tanks to rot out and ruin the room below.

I know that proper maintenance likely would have eliminated the tanks rotting out but these came with the house and were 15 years old when I got them. It was more of piece of mind.

Have not really noticed a difference in the gas bill but that was not a factor. Install was about $5k and already had 3/4" gas line in the area so no new lines had to be run.

Otherwise, satisfied with the purchase.

Gas supply is important. Make sure you have proper sized lines and pressure. We installed rennai this summer and everything was fine until we started running the gas fireplace and furnace. WH occasionally won't fire up. The plumber used an either 3/8" or 1/2" flex from the 3/4 supply to the WH. So much for professional installation. I have to try and get him back to correct it now. Instructions are clear that it needs to be 3/4".

I have 3 of them in 3 separate houses. All propane.
Large Rinnai on outside north facing wall has been flawless since I bought the house 5 years ago. The only problem I've had is freezing inlet piping solved with added insulation and heat lights.
I had one retrofitted to a 3 bedroom, 2 shower cabin in Colorado to replace an electric tank heater. Wall mounted inside the house vented through the wall its mounted on. Also a large Rinnai model. I think it cost about $5000 all in which included running a propane supply line from the crawl space up an inside wall to the second floor utility room. The vent on this is a concentric PVC pipe which brings in combustion air and exhausts hot air.
I had a propane tank heater in a 2 bedroom/2 shower house on our property that started leaking. I bought one of these https://www.eccotemp.com/eccotemp-i12-indoor-4-0-gpm-natural-gas-tankless-water-heater/.
I installed it myself on a wall where the old tank heater was. Exhaust runs through a 3" dia hole I drilled in the wall the unit is mounted on. You can't just use the vent from the old heater so this is important. Combustion air comes from the room the unit is installed in. I am very happy with the eccotemp and have had no problems with water supply for 2 simultaneous showers. I noticed that the minimum flow on the eccotemp unit is not as low as the Rinnai. It has a small diameter propane line feeding it. Same as the tank heater.
Maintenance is flushing annually with vinegar using a bucket and submersible pump.
The vents on all three are forced air.
Hope this is of help.

For reference we were quoted $4700-5200 for tankless without messing with the incoming gas line. Well we did have one at $7200 but that was an outlier.

Tank heater quotes have been $1500-2500 depending on a few options. The one in my house is over 15 years old so it is time to replace before it starts having issues

I had one when I lived in midland. It had a 110v power cord. Was nice during the '21 freeze to plug into gen and have hot water.

Had a Navien installed in our new Barndo. We really like it. Just remember, they're all "Smart" appliances. LOL

https://www.navieninc.com/residential/tankless-water-heaters

Dont have one, but only thing I have to add is one of my real estate inspectors used to say make sure that you had soft water or a water softener system to keep them from getting Ca buildup and failing. Pretty much a brick at that point per him.

One thing I have read (have looked into making this switch as well) is that you want to make sure you don't have hard water, because it will cause earlier failure than normal. At least that was one of the common comments I saw a while back when i was really thinking about doing something. It makes sense, because hard water will calcify everything around it, which does eventually cause problems with appliances. Anything heated exacerbates the issue.

I have a water softener now, so that issue wouldn't be on the list for me anymore. I just can't get myself to ditch a perfectly good traditional heater yet, even though it's in the damned attic where I think no water heater should ever be located.

GeorgiAg said:

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True but set the temp at max and adjust the knob at the showers. I can't remember the size of the heater but it was enough for two showers.

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Adjusting the temperature on a tankless water heater doesn't provide more hot water (that does work for tank systems, but not tankless).

The water heater has a maximum BTUs it can produce. Once you achieve that, regardless of the temperature setting, you're at the max.

The max temp was around 140 if I remember correctly. That will melt your face off.

A comfortable shower is at 100 degrees or so. When I was the only person using hot water for a shower I'd set it at 100 or whatever temp I like and just open the hot water valve all the way. No cold water.

If other people are using hot water, set the temp at the max and that way you use less hot water and off set with more cold water to "cool" it down by opening the cold water valve. Since you are using less hot water pressure, that gives others access to hot water that is so hot they don't t need that much of it either. They also need to mix with cold.

It usually wasn't an issue. I had an 1886 Victorian 3 bedroom plumbing retrofit with only two bathrooms (not even a half bath) and a kitchen sink. One bathroom had a shower and a tub. The other had a shower only. Only other hot water was the washing machine and dishwasher. There were a few times I got annoyed with not setting the temp high enough and somebody kicking something on.

I also remember having to have all hot water off before you could change the temp setting. It's been a while since I lived there, but I think that's right. It has it's drawbacks, but I loved the unlimited water and that it wasn't heating anything when I wasn't there.

From what i understand, bigger houses use more than one unit, so that's not an issue.

GeorgiAg said:

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The max temp was around 140 if I remember correctly. That will melt your face off.

A comfortable shower is at 100 degrees or so. When I was the only person using hot water for a shower I'd set it at 100 or whatever temp I like and just open the hot water valve all the way. No cold water.

If other people are using hot water, set the temp at the max and that way you use less hot water and off set with more cold water to "cool" it down by opening the cold water valve. Since you are using less hot water pressure, that gives others access to hot water that is so hot they don't t need that much of it either. They also need to mix with cold.

It usually wasn't an issue. I had an 1886 Victorian 3 bedroom plumbing retrofit with only two bathrooms (not even a half bath) and a kitchen sink. One bathroom had a shower and a tub. The other had a shower only. Only other hot water was the washing machine and dishwasher. There were a few times I got annoyed with not setting the temp high enough and somebody kicking something on.

I also remember having to have all hot water off before you could change the temp setting. It's been a while since I lived there, but I think that's right. It has it's drawbacks, but I loved the unlimited water and that it wasn't heating anything when I wasn't there.

From what i understand, bigger houses use more than one unit, so that's not an issue.

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I understand the concept, and what you're describing works for a tanked system in that you are starting with a larger volume of hotter water before the demand hits.

My point is, that strategy does not work for a tankless system, as there is no stored water. It's not the rate of water that limits the tankless system, it's the rate of heat the system can put into the water that limits the system.

If you set the system at the lower temperature, the tankless unit will be able to heat higher volumes of water to that temperature. If you set it to a higher temperature, it will heat lower volumes to that temperature. This negates the "blending at the point of use" concept that works for tank systems for short term demand.

If you don't believe me, check out the math below.

Let's take this guy here:

https://www.lowes.com/pd/Rinnai-Super-High-Efficiency-Plus-8-GPM-160000-BTU-Indoor-Natural-Gas-Tankless-Water-Heater/5014873335

Says it is 9GPM and 160MBtu/h.

160MBtu/h will heat 70F water to 105F water at 9 gpm. That's its max rate.

If you change the temperature setting to 140F, that unit will only be able to flow 4.5 gpm before it hits its maximum 160MBTU/h output. That's because each gallon of water requires more heat to get to the higher temperature.

At 140F, blending 70F water at the point of use to get 105F will give you a 50:50 mix of hot and cold water. Well, 4.5gpm + 4.5gpm = 9gpm.

So whether you set the tankless system to 105F or set it to 140F and add cold water later, at the end of the day, you end up with 9gpm of 105F water delivered to those showers. Which means you should just set the system to the hottest temperature you would expect to need.

ETA: I have had a tankless system for about 10 years now, and I love it. I do a traditional hot/wet shave, so ours is set to 130F for that reason.

CapeAggie89 said:

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We moved to tankless for two main reasons. 1. Unlimited hot water (teenagers). 2. Not having 80 gallons of water in the attic sitting there waiting for the tanks to rot out and ruin the room below.

I know that proper maintenance likely would have eliminated the tanks rotting out but these came with the house and were 15 years old when I got them. It was more of piece of mind.

Have not really noticed a difference in the gas bill but that was not a factor. Install was about $5k and already had 3/4" gas line in the area so no new lines had to be run.

Otherwise, satisfied with the purchase.

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We had very similar reason for moving to tankless. Had 80 gallons in the attic waiting to fail (we figure our water heaters were upwards of 25 years old - original to the house) so it was just a matter of time so did the pre-emptive replacement. Got the recirculating feature with timer so recirc hot during morning and evenings for quick hot water in showers and sinks. Turn that off during the middle of the day and middle of the night. Pretty cool feature.

Had to replace one standard one recently and decided to replace the other at the same time for a discount.

Plumber talked me out of it due to having to increase the gas line size, the annual maintenance, upfront capital costs, possible freezes, etc. (basically he did not like them).

Stuck with standard heaters since they are basically maintenance free.

We have one. I wish we had elected to get two when we built, one on each side of the house. One story house and the distance across the house means running the water a long time to flow in my kids rooms.

Anyone have a referral for who you would recommend to do this kind of work in N Houston/The Woodlands?

Thinking about making the switch with 100 gallons of water sitting in my attic in two aging tanks.

I used the Hot Water guys, all they do is tankless, but not sure if they are the cheapest.