Flushing a Tankless Water Heater

[Mike Henderson]

My wife and I are not young any more and have to contemplate our mortality. My wife has been bugging me for a while to document how to do some things around the house, such as how to turn the water or gas off in case of an emergency. One other issue was how to flush the tankless water heaters.

So I put together a number of web pages the document each item, going step-by-step so that she could follow the directions if I wasn't there. Most of the items are specific to our property but I thought the one on flushing the tankless water heater might be of interest to others. The web page is here (http://www.mikes-woodwork.com/SerranoTankless.htm).

In case you're not familiar with tankless water heaters, they require annual flushing with a weak acid (vinegar) to remove any build up of mineral deposits on the tubing in the heater. It's not difficult to do, and it's important to efficient operation and long life.

Mike

[Erik Loza]

Thanks for posting this, Mike. We have a Rinnai and I was wondering about the procedure.

Erik Loza
Minimax USA

[Greg Portland]

Looks good. You may want to document the wrench required to open the valve ports.

[Steve Peterson]

Thanks Mike, the procedure was documented very well. It is interesting to see the water heater on the outside of the house. Must not get very cold where you are at.

We have a tankless water heater in a vacation home and I have a plan to install valves to allow flushing the unit. My backup plan is to never flush it in hopes that it will suffer an early death. It is the worst appliance that I have ever owned. It shuts itself off with error messages all the time, including in the middle of a shower. I want to go back to a normal tank style heater that you never have to worry about.

Steve

[Erik Loza]

Steve, just curious: What brand is yours?

We have had zero issues with ours. Great investment, in fact.

Erik Loza
Minimax USA

[Mike Henderson]

Looks good. You may want to document the wrench required to open the valve ports.
Nothing special. I just use a pair of pliers if they're too tight to turn by hand. I think I said that in the procedure.

Mike

[Mike Henderson]

Steve, just curious: What brand is yours?

We have had zero issues with ours. Great investment, in fact.

Erik Loza
Minimax USA
Me, too. Never a problem. Mine is a Rheem. I'd never go back to a tank. It's just wonderful to never run out of hot water, and my gas bill went down when I put the tankless in.

[Side note: When we had a tank, I'd get in the shower and my wife would put stuff in the washer. By the time she went to take her shower, there was no hot water. Unhappy wife! Remember that the secret to happiness is "Happy wife, happy life."]

Yes, it never freezes around here (southern California).

Mike

[Mark Bolton]

I also have a Rheem (mine made by Paloma) and other than a circuit board that had to be upgraded, which was sent to me with a phone number for an open ended phone call with verbal step by step instructions (phenomenal customer service) I have had zero trouble from the unit itself. The issues I did have were my own. I initially tried to run the heater (rgt53 lp) on two 100lb bottles in a remote home. In cold winters this wasn't enough gas and we would occasionally get error messages I the control panel. Adding a third empty cylinder solved everything.

I would never go back to a tank type heater either. My only beef with some models can be too high a cut-in flow rate and I do worry sometimes about wear and tear if you live in a house with lots of short cycles (like people who insist on turning both hot and cold on for a quick hand wash when no system other than recirc will get you hot water anyway). But the newer models are amazing.

We've installed several for customers the latest being a Navien.

Thanks for the post. I'm iverdue for a flush.

[Jim Becker]

Thanks! We have two tankless systems in our home...excellent information to have!

[Brandon Davie]

We had a tankless installed in our last house. It over heated and caught fire. Thankfully I was around when it happened. Cut the power, grabbed the extinguisher but the heat caused the pipe to bust out and it put the fire out for me. Then I had to cut the water off to prevent my laundry closet from flooding even more.

[Bill Cunningham]

Thanks for posting this, Mike. We have a Rinnai and I was wondering about the procedure.

Erik Loza
Minimax USA

I installed a Rinnai about 4-5 years ago, and love it.. Mine came with bypass flushing valves. We are on a lake based water supply, and about the only thing in it is added chlorine. I did have a oil fired water heater that was very fast (54deg-130 shut off in 17 minutes), but it burned $600.00 worth of oil a year. The Rinnai uses 14 cents worth of N.Gas a day ($51.00 a year) Showers/dishwasher/etc..e. Lake water is very soft, and we don't even get a mineral deposit of anykind on anything. So, I have not had to flush it at all.. I don't know why anyone would want to keep 40-50 gallons of water constantly hot in case you need it..

[Steve Peterson]

Steve, just curious: What brand is yours?

We have had zero issues with ours. Great investment, in fact.

Erik Loza
Minimax USA

It is a Bosch AquaStar 250SX. The reviews are not very good. It appears that people either love tankless water heaters or they hate them. I am in the second group, but maybe it is just this brand.

I cannot think of a single characteristic (except small size) where it performs better than a tank style heater. I don't believe that there is a cost savings after taking into account the extra upfront cost. We cannot use a low flow showerhead because it doesn't use enough water for the flow detector, so the only option is a less efficient showerhead. Two showers and a dishwasher running at the same time will produce lukewarm water. And it is nearly impossible to maintain a comfortable shower temperature. It switches from too hot to too cold, so you have to constantly adjust the temperature.

I miss the old fashioned tank style water heater.

Steve

[Mike Henderson]

It is a Bosch AquaStar 250SX. The reviews are not very good. It appears that people either love tankless water heaters or they hate them. I am in the second group, but maybe it is just this brand.

I cannot think of a single characteristic (except small size) where it performs better than a tank style heater. I don't believe that there is a cost savings after taking into account the extra upfront cost. We cannot use a low flow showerhead because it doesn't use enough water for the flow detector, so the only option is a less efficient showerhead. Two showers and a dishwasher running at the same time will produce lukewarm water. And it is nearly impossible to maintain a comfortable shower temperature. It switches from too hot to too cold, so you have to constantly adjust the temperature.

I miss the old fashioned tank style water heater.

Steve
If my tankless did all that, I'd hate it too. The Rheem heats water at a pretty low flow. I shave with a low flow of hot water and I'm the only user on the system and I get constant hot water. I have a low flow shower head (I guess everyone in CA has those) and have no problems with constant temperature water.

Tankless is an old technology - you'd think all the manufacturers would have worked out the bugs by now.

Regarding two showers and a dishwasher running at the same time and the tankless not being able to keep up - tankless heaters are made with different maximum flow rates. If you draw more gallons per minute (GPM) than the tankless is rated for, you will not get constant hot water. You have to size the tankless to the expected maximum flow.

I agree that the cost to switch is high - I had to reroute plumbing and add an electrical circuit. But I wanted to recover the space used by my tank style hot water heater. I may, or may not, ever recover that up front cost, but I'm glad I made the switch. My tankless works well and I like never running out of hot water.

Mike

[ken masoumi]

I realized my question may be considered as highjacking this thread so I deleted it.

[Erik Loza]

It is a Bosch AquaStar 250SX. The reviews are not very good. It appears that people either love tankless water heaters or they hate them. I am in the second group, but maybe it is just this brand.

I cannot think of a single characteristic (except small size) where it performs better than a tank style heater. I don't believe that there is a cost savings after taking into account the extra upfront cost. We cannot use a low flow showerhead because it doesn't use enough water for the flow detector, so the only option is a less efficient showerhead. Two showers and a dishwasher running at the same time will produce lukewarm water. And it is nearly impossible to maintain a comfortable shower temperature. It switches from too hot to too cold, so you have to constantly adjust the temperature.

I miss the old fashioned tank style water heater.

Steve

Wow, what a bummer. I am sorry to hear all that because, to be honest, ours has improved the hot water situation in the house at all levels. We have a walk-in shower upstairs with two heads. Wife and I can shower for as long as we like and no hot water issues. I routinely run the dish washer and the washing machine at the same time, no issues there either.

Two things I will say, though:

1.) The unit we bought was rated slightly higher than we thought we would ever need in terms of BTU's. Figured "Why not?".
2.) We have no water pressure issues on the supply side. The City tore up our neighborhood and replaced all the old iron pipe with new stuff. And when we remodeled the house, I had every piece of galvanized pipe replaced with PEX, so there are no flow issues on the suplly side.

No idea if either of those are/might be a factor in your case but I can tell you that there is nothing not to like about the technology, itself. Just my 2-cents as always.

Erik Loza
Minimax USA

[Steve Peterson]

If my tankless did all that, I'd hate it too. The Rheem heats water at a pretty low flow. I shave with a low flow of hot water and I'm the only user on the system and I get constant hot water. I have a low flow shower head (I guess everyone in CA has those) and have no problems with constant temperature water.

Tankless is an old technology - you'd think all the manufacturers would have worked out the bugs by now.

Regarding two showers and a dishwasher running at the same time and the tankless not being able to keep up - tankless heaters are made with different maximum flow rates. If you draw more gallons per minute (GPM) than the tankless is rated for, you will not get constant hot water. You have to size the tankless to the expected maximum flow.

I agree that the cost to switch is high - I had to reroute plumbing and add an electrical circuit. But I wanted to recover the space used by my tank style hot water heater. I may, or may not, ever recover that up front cost, but I'm glad I made the switch. My tankless works well and I like never running out of hot water.

Mike

Ours is a 143K BTU unit, supposedly good for 6.35 gpm. It may be slightly less since it is at 5000' elevation. It is good to know that there are other brands out there that work like they are supposed to.

Steve

[Jim Becker]

I had a Bosch Aquastar 250 in our addition, but replaced it last fall with the same Paloma (Wai Wela) I installed in the older part of our home after a hurricane flooded out our basement a couple years ago. There is no comparison...the Paloma performs in a stellar way. The Bosch didn't last and support was terrible. My only (minor) complaint is that the newer one is noisier than the older one and that's noticeable since it's in living space. (2nd floor laundry room) The "endless" hot water is enjoyable and we're only burning natural gas to heat water while we are actually using hot water. Does it cost less in the end? It depends. Because we had to have a special "shortie" tank type water heater due to head room, it's replacement cost was only a hundred dollars less than the tankless unit that replaced it. So for us, we are saving money.

Oh, the other thing I like about the Paloma I have is that it vents with PVC. That was a requirement to even put one in the older portion of our home. The Bosch required very expensive stainless steel venting. Being able to use PVC brings the cost factor way down.

http://img.photobucket.com/albums/v646/a-j-adopt/IMG_0925_zpsa765c7d1.jpg

[Colin Giersberg]

We have a Rinnai and we love it. My wife always took long showers (still does) when we had a tank type water heater. After she would get through with her shower, I would wait 30 minutes or more for the water to heat back up. Once I would get in the shower, she would come in to the bathroom to brush her teeth. She always turns the faucet on full blast, and needless to say, my hot water did not last as long as my shower did. We finally decided to get a tankless unit. We have not had any issues with running out of hot water, although when the washer runs water again, the temperature does drop in the shower for about 5five seconds or so, but then it warms back up quickly. When the April 27, 2011 tornado hit near us, we lost power for a week. The tankless heater is nice when you have no household power. We ran a 5500 watt generator the entire time and just plugged the tankless unit into it. Still had all the hot water we wanted. I can't imagine ever going back to a tank type unit anymore.
If anyone is considering a tankless water heater, check with your city or county water utility. They may offer a tankless water heater for a substantial discount. We use Limestone County Water and Sewer and we bought the Rinnai whole house unit for $750. We did have to get our gas line replaced because it was too small for the gas log fireplace and the Rinnai to operate at the same time. After replacing the gas line, they sent out two employees to replace the gas meter since this was too small as well. After it was all said and done, we paid approximately $1450 for everything. I think it could have been done cheaper if we could have gotten the right plumber to begin with. The first plumber came out and hung the tankless unit, but he could not install the gas line (not licensed for that) and he would not install the vent pipe. That was $100. The next plumber (different company) removed the undersized gas line and installed the larger size. That was $600. There was no cost to replace the gas meter. The Rinnai cost $750. I learned a lesson there. The second plumber was able to do all the work, but we just didn't call him first.

[Bill Cunningham]

Our Rinnai has a digital display on the front, and When running the dishwasher, we set it for 140F. When in the shower, I set it for 104 or 106 (depending on my mood) Open the shower full hot, and step inside. The Rinnai monitors and controls the heat, and it never budges no matter what else is turned on.. Ours is 180kbtu input and draws 3 amps on a standard 3 prong plug so it can also be plugged into the generator on a power failure. They ain't cheap, (mine was 2k installed [after eco grants] but because I didn't have a outside facing wall to mount it on I needed a special through the roof vent that handles both intake and exhaust) but over oil I'm saving $550 a year based on oil prices in 2008, So the payback time was under 4 years. Well worth the investment..

[Colin Giersberg]

We have our Rinnai installed in the garage, with the vent making a 90 degree bend and exiting out of the wall. This did require extending the natural gas line. This is partly why we had to have our gas lines up-sized from the meter to the gas fireplace. After that, the pipe is back to the regular size supply line. Fortunately, we have a water line near the Rinnai, so we didn't have to have much plumbing done.