Info and Advice on Tankless Water Heaters

[JoyfulNoise]

yup, the 5 gallon bucket was the temporary solution to the condensate drain until the next time I make it out there to help run it properly. It's been that way since February and he said it has never gotten fuller than about .25"
The condensing units are negligibly more expensive but on average about 10% more efficient. The exhaust of the condensing units is significantly cooler which allows for the use of alternative (typically pvc) vent pipe.
The non condensing units typically produce the condensate as well but in the vent pipe. The condensate formed by both types of units is acidic (hence the need for stainless and a horizontal section with drain so it does not drip back into the unit)

Thanks for the info.

I’ll have to talk to my plumber about condensing versus non-condensing. Because I have the HVAC air handler in the closet, there’s already a condensate pipe available that could handle the drip from both units. So I’ll see what they typically install. Like a lot of trades, these guys usually have only a few options they prefer to install and don’t like to get outside their comfort zones … but interesting to note nonetheless.

 

[Ahultin]

Thanks for the info.

I’ll have to talk to my plumber about condensing versus non-condensing. Because I have the HVAC air handler in the closet, there’s already a condensate pipe available that could handle the drip from both units. So I’ll see what they typically install. Like a lot of trades, these guys usually have only a few options they prefer to install and don’t like to get outside their comfort zones … but interesting to note nonetheless.

Make sure you check where it discharges if you go that way, the condensate is acidic and will etch concrete/stucco and kill plants lol. If it discharges somewhere sensitive you'll want to account for the cost to add an inline neutralizer.

 

[Flying Tivo]

Never imagined it could be acidic, i will use my test kit on my condensate and report back.

 

[Kaylee34]

I'll add in that IMO tankless is the way to go for most people. Rinnai is not a bad brand. They were one of the first to come out with tankless if memory serves correctly. I'd also go condensing if possible. Some units will require fresh air intake so that's something e;se to discuss with the plumber. I helped a friend convert to tankless this spring and their's required two 2" PVC vents. One for intake and one for exhaust. Venting through the roof wasn't an option for them so we went through the sidewall of the house. You hardly notice the vent pipes.

If my own water heater wasn't just a couple years old, I'd be replacing it with tankless. If I still have this house wihen it's time to swap, it will be tankless.

 

[JoyfulNoise]

Never imagined it could be acidic, i will use my test kit on my condensate and report back.

All combustion gases are acidic when condensed. The burning of fuels (NG, propane, fuel oil) creates smal amount of NOx and SOx compounds. When those dissolve into the water created by the combustion process, the condensate becomes very low pH and corrosive. Most combustions processes are designed to not be condensing because of this. In the case of these heaters, there are two heat exchangers and the flue gas is used to preheat the incoming water in a small secondary heat exchanger before getting fully heated by the primary exchanger. This increases efficiency but caused flue gas to condense.

There is a Pentair gas heater model that uses this principal to reach 90% efficient but the heat exchangers (there two) are titanium and you need to neutralize the condensate. It also costs nearly twice as much as a basic MasterTemp so not really worth it.

 

[Flying Tivo]

All combustion gases are acidic when condensed.

No need to test then!

 

[JoyfulNoise]

This thread can close but wanted to say thanks to everyone.

In the end, I'm going to have to go back to a standard 50-gal tank heater. After having three plumbers out to look at it, only one of them would do the job and he wanted to punch a hole in my wall to put a new PVC exhaust/vent line out of because he wasn't going to use the existing galvanized exhaust that is common between the current hot water heater and the HVAC system. He was too afraid that the tankless heater exhaust would rot it out and he did not want the liability. All them spit-balled an estimate over $4,500 to $5,000. Doing a new exhaust would have triggered an HOA review because the wall it is on faces the common street area and I did not want to deal with the HOA.

A standard tank heater will cost me right around $1,000 total (all new plumbing back to the copper pipes in the wall, labor, install, startup and haul away the old heater). It'll have to be good enough ...

 

[JamesW]

Just remember to periodically check for leaks to catch anything before it becomes a big mess.

 

[JoyfulNoise]

Just remember to periodically check for leaks to catch anything before it becomes a big mess.

Yeah. I’ll be installing a wireless water alarm in there. There are several ones that don’t need WiFi connectivity. I’ll just install the detector and then add the alarm to my front closet where all my home alarm gear is.

 

[Bperry]

Maybe put a drip panel to at least catch some slow leaks.

 

[Dirk]

Only read the last few posts, so don't know if this was mentioned. I like the idea of tankless, but I like much more the fact that my water heater is storing a 50 gallon supply of readily available emergency water. There are other ways to store water (which I also do), but the water in the tank is fresh and constantly being turned over. So that's 50 gallons I can use, if I ever have to, before having to resort to toilet tanks!

With today's declining infrastructures combined with ever-increasing threats to our utilities, it's not really as much of a hypothetical anymore as it once was...

 

[JoyfulNoise]

Only read the last few posts, so don't know if this was mentioned. I like the idea of tankless, but I like much more the fact that my water heater is storing a 50 gallon supply of readily available emergency water. There are other ways to store water (which I also do), but the water in the tank is fresh and constantly being turned over. So that's 50 gallons I can use, if I ever have to, before having to resort to toilet tanks!

With today's declining infrastructures combined with ever-increasing threats to our utilities, it's not really as much of a hypothetical anymore as it once was...

Agreed. Our power, while not the cleanest in terms of frequency drift (we’re at the end of the line for utilities), is surprisingly reliable. If we have one outage a year, that’s a lot and we’ve never had an outage go more than a few hours. But, the nice part about a gas-fired tank heater is that you don’t have to worry about supplying electricity to it. You can do a backup battery system for a tankless heater (to power the control electronics) but that’s only going to keep you going for so long.

So I’ll just suck it up and go old school and burn my dinosaur juice … 40,000 BTU/hr is a drop in the bucket compared to my pool heater

 

[Dirk]

Agreed. Our power, while not the cleanest in terms of frequency drift (we’re at the end of the line for utilities), is surprisingly reliable. If we have one outage a year, that’s a lot and we’ve never had an outage go more than a few hours. But, the nice part about a gas-fired tank heater is that you don’t have to worry about supplying electricity to it. You can do a backup battery system for a tankless heater (to power the control electronics) but that’s only going to keep you going for so long.

So I’ll just suck it up and go old school and burn my dinosaur juice … 40,000 BTU/hr is a drop in the bucket compared to my pool heater

Yep, same rational I use for my stove. I like cooking over gas, but I especially like being able to cook without electricity. I can't afford to be a full-on survivalist, but there are a handful of things that can be done relatively inexpensively (extra/redundant: batteries, radio, water, food, cooking, medical, etc). Not intending to turn this thread, just pointing out that there was another factor when considering going tankless, or for that matter when purchasing/replacing any appliance or integral home/pool system.

 

[Dirk]

Our power, ..., is surprisingly reliable.

Same here, knock on wood. But I'm in CA so it's just a matter of time before rolling blackouts come my way... I'm contemplating a whole-house gennie. I have PV solar, so could go battery, but I think that'd only get me through a day or two. Between the fat water heater and some extra food, and the natural gas, a gennie would fill in some of the gaps, especially for the pool. I can't protect myself from Armageddon, but my goal is to be able to combat our government's ineptitude for a few weeks at a stretch.

Not to mention I'll be the "best friend" of all the surrounding neighbors if I can keep the lights on, the soup warm and the beer cold!

 

[wireform]

I'm in full agreement with going the route you chose but I'd consider a mixing valve setup right above the tank which makes it most efficient by mixing the water to a set temp and sending that temp out throughout the home. Obviously the temp you chose is a little hotter then you can tolerate thereby leaving more water in the tank so the reboil is far shorter time wise but also will seldom leave you without enough hot water. I have one on my indirect hot water set up so when the grannies come for the weekends and fill bath after bath they can't deplete the hot water as fast.
https://www.supplyhouse.com/Resideo...alve-8-SS-Corrugated-Hose-Connector-Lead-Free