On demand hot water service

For those who work with these or have one in use.

Are they actually saving money?

Do they make enough Hot water?

Considering one for the Compound.

Steve

I've got 2 and they are WONDERFUL! All the water I want all the time.

Since I designed the plumbing system around them and never had traditional heaters in this house I couldn't say if they saved money, but that's not the reason I got them. My wife has a 80 gallon tub which would have used up all the hot water in a traditional HWH system.

There is a minute amount of delay time when you turn them on before the water gets hot and I mean minute. It's a lot less time than it takes the water to get from the HWH to the tap in a traditional system BUT that means it's better if you design the system around HWH rather than just replace a traditional one. If you already have a long water line run and add any time at all to it then it might be a bother.

The plumbers and the manufacturers typically put them in the outside walls and give you shorter water line runs to make it super responsive.

Outside walls means you don't need very expensive, double walled, exhaust piping. I'm talking $25 a foot piping. We just went thru weather near zero degrees for days on end and freeze up wasn't an issue in the outside wall installation.

Is yours gas powered or electric?

I'm betting Carguys house is slab on grade, thus the outside wall installation. A regular gas HW heater doesn't need double walled exhaust piping(although local laws vary) and a power vented one is easily exhausted with PVC. I'm curious as to the intial cost, warranty, and size/make. I've seen a huge price and performance difference between the various makes, but, as noted above, by using multiple units(sized properly) they can be placed where you need them. Like Carguy stated, they may be better suited for a new build. I've installed a couple but I'm not a fan of them. But the customer is always right! IMHO, a quality, power vented tank, w/electronic ignition, positioned to minimize run length and well insulated hot water lines, is tough to beat.

A coworker priced one a while back and the payback was like 20 years.

The plumber who replaced my gas water heater last year indicated a tanlkelss water heater would cost well over $3000. Which I thought was high.

My son is re-habbing an old home and has installed one. He loves it, says the cost was about 800.00. Off brand, installed by a licensed plumber who is a close friend. YMMV.

Electric won't be vented to the outside because there would not be any combustion! Just like a regular electric heater.

I replaced a 15-year-old tanked heater with a gas fired Rennai tankless direct-vent because it was only a little more expensive than it would have been to have a stainless steel flue liner installed in the existing masonry chimney that the old heater was vented to. The flue liner would have been $1100 and the new heater was about $1600 installed for one sized to fit a 4-bedroom, 2-bath house.

So far, the Rennai has saved a little in CF of gas over the old heater, but not a titanic amount.

It definitely makes plenty of hot water. You can stay in the shower for hours and never run out, and even do a load of laundry at the same time. It takes about 90 seconds of running the shower to get the heater's attention, get it up to temp, and deliver hot water to the second-floor bathroom. However, it has a flow meter that turns it on, and that is set to ignore small volumes of water moving through it. This is so when you turn on single-lever faucets in the default middle position just to rinse something off or fill a glass, it doesn't immediately fire up just to shut down again seconds later. So it you want hot water, the way to do it is turn on full hot so it wakes up and gets to work right away, then turn the temp down to what you want.

When I first had it, I had the output temperature jacked pretty high because I thought it would have to make less hot water. That was counterproductive, because if you only wanted warm water, the volume draw would fall below the heater's "ignore" threshold, and it would shut down production. I lowered the water temp (safer anyway) and that has stopped happening.

Overall, I like the unit, and as I said, the main reason I did it was to avoid an expensive job that still would have left me with a 15-year-old water heater. It does take some change in your usage profile to adapt to how it works, but in a family of 4, we can all take back to back showers and nobody freezes. But I would not buy one expecting it to pay for itself right away with reduced energy costs.

I have one. Gas not electric. My only complaint is that the bathroom on the far side of the house takes a long while to get hot water. Not due to the water heater, but due to it's placement and length of plumbing between it and the bathroom. The heater is on an outside wall adjacent to my closet. Master bath gets water right away. No idea if it is really cheaper or not.

I have one. I just installed it in December, so I'm not sure the savings. My old one was about 20 years old, so it was due time to replace it. That and my chimney is collapsing, so I want to get rid of the chimney completely and get something I could vent out of the foundation. I bought it online for $675 with the stainless steel horizontal vent kit. I then got $150 rebate from my power company, and 1/3 of the purchase price back on my taxes, so it seemed dumb to go any other way. My only complaints are that it takes maybe 15-20 seconds longer to get hot water (not a big deal to me) and that the one that I got doesn't have a variable gas valve, so the water is hotter in low flow situations that it is in high flow. Also, it's advertised as a 6.3GPM, but if you try to fill the bathtub at full blast it can't quite keep up. Turn the hot water knob about 3/4 open and it does a great job. I just like the fact that I can stay in the shower as long as I want, and we can take consecutive showers and never have to worry about running out of hot water.

Only issue with mine besides the wait time for hot is when washing dishes in the sink I cannot shut off the water as I then have to wait for reheat to rinse off dishes.

My house is slab but that wasn't the reason for the outside wall installation, it was the heat these things put off and the double walled flue needed.

Every dissappointed user I've met has had an electric one. The electric ones can't react quickly enough to give you hot water fast.

I've never had an issue with waiting for hot water and 90 seconds is WAY longer than I wait, but that could just be a sizing issue. I bought big & fast. I've got 2 Rinnai R85s.

They are best used in a new installation. Often the existing water heater is located in the center of the basement near a chimney. You will most likely mount the new heater on a wall so the venting is closer to it's end point. That means you will have to bring the existing water lines to the unit. You will also have to bring the gas line to it. Bear in mind these things require 200,000 BTUs of gas where as the old conventional WH only requires 40,000 or so. You may be looking at increasing the gas main and sometimes even having the gas meter resized. Typical refit install is around $2500.00 here in the northeast, mostly because of these issues. They work great in additions. I love installing them in closets where you can vent right out of the side of the building. They also require periodic flushing with a descaling compound or vinegar solution to clear the build up of mineral deposits on the heat transfer plates. I wouldn't put one in my house unless it was for an in-law apartment over the garage and the old existing water heater was way far away. If you want cheap green hot water, look into solar. Expensive up front but fantastically efficient once it's in.

aussiesmg wrote: For those who work with these or have one in use. Are they actually saving money? Do they make enough Hot water? Considering one for the Compound. Steve

1) yes, it saved us about 30%.

2) yes, with a caveat. Ours was an industrial 360v three phase unit, but our plumbing was also 1" and 1.5" which flowed a lot. There were several times that a long, hot shower would exceed the duty cycle of the heater and it would shut off for about 30 seconds. Not pleasant in the shower. But for a standard 1/2" water conserving shower head it probably would have been fine.

We finally replaced it with another brand of heater and it eventually did the same thing, so we had to go back to a regular tank heater, thus negating any savings that might have been.

For 90% of things, its great. Instant hot water, lots of it, but for high demand its just not really an option.

It might not be an option for an electric version, but I've had 16 people in the house with all of them taking showers and filling the tubs one right after another with never an issue, but I've got gas.

The part that I see a drawback is the little jobs.

I put the smallest electric Bosch unit from Menard's under the bathroom sink in my building. The first one was defective & didn't shut off the heating element. It got so hot it caused the CPVC line to rupture.

The 2nd one has been working ok. There isn't much adjustment with this unit, you only get full-power or 1/2-power & a flow adjustment. And even right under the sink you still have to wait for it to get warm, then turn it down quickly before it gets scalding hot.

Due to the layout of things, it was either one of these, or a tiny normal electric heater. This takes much less space, and I'd sure hope it's cheaper to operate, especially no more use than it gets.