More Musings of an Energy Nerd
My house has a tankless gas-fired water heater. I’ve owned several brands over the years, including an Aquastar and a Bosch, but my current model is one made by Rinnai.
The standard advice for owners of a tankless gas water heater is to clean out the mineral deposits that build up in the water heater pipes—a process called descaling—once a year. I suspect that annual descaling isn’t necessary, except perhaps in regions of the country that have very hard water. I have owned my Rinnai heater for seven years, and I’ve never performed any descaling.
Frankly, the descaling process sounded intimidating, so I followed the common-sense dictum, “If it ain’t broken, don’t fix it.”
About two weeks ago, however, my wife and I noticed that the rate of flow through the water heater had significantly diminished. We were still getting hot water out of the tap, but it wasn’t flowing very quickly. I knew what I had to do: it was time for descaling.
You may be wondering…
If you own a gas-fired tankless water heater, you may have several descaling questions.
Do you need to perform descaling? If so, how often? Do you have to hire a plumber to perform the work, or is it possible to do it yourself? Assuming it’s possible, how complicated is it?
Don’t be intimidated
First, the good news: the process wasn’t as difficult as I anticipated. For me, the key was to buy a descaling kit. My kit cost $135; I purchased it at Amazon.com. That’s significantly less than most plumbers would charge to descale my water heater—and the kit can be used for years and years.
The kit I brought is sold under the Kelaro brand name, but other…
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10 Comments
Thanks Martin! Though I don't have a tankless water heater several friends and family members do - and I'm sure they have no clue they should descale periodically. I'm going to bundle one of my small sump pumps a bucket and washing machine hoses together to loan along with a link to this article so they can execute the procedure. There are so many house maintenance chores that average homeowners aren't aware they need to do (or have done by a service pro) like changing HVAC filters, servicing water softener / filter systems and changing out the anode rod in a heat pump water heater.
HiYa Mike Guertin,
You are so right about maintenance chores that homeowners--often unwittingly--don't do. Jon Harrod wrote a great article about that and the comments are equally valuable: Home Maintenance Tasks You’re Probably Not Doing (and Should Be).
Mike,
Which brings us back to the idea championed several times over the years in FHB articles of each house having a manual.
I'm afraid manuals don't help unfortunately. We need a household dashboard display on the front of every refrigerator alerting owners that something is due for maintenance. A 'Check Engine' or "Maintenance Required" light perhaps.
I made manuals for each house I built or rebuilt. They didn't seem to help. The owners of the house I sold in November of 2022 contacted me this past Feburary with a few problems. Bathroom mirrors were fogging up a lot and not drying and the heating system wasn't able to get the house above 65F were the two main things. They hadn't followed the Maintenance Checklist with the monthly check of the ERV filters and filters at the indoor heat pump units. A lot of dust accumulated in 15 months.
I guess we can just keep trying.
Another complicating factor: Because maintenance advice is sometimes self-serving (have you ever had a car dealership's service department tell you that your vehicle needed ball joints or brake pads -- only to learn from another mechanic, one you trust, that your ball joints or brake pads are fine?) -- including, perhaps, the advice to remove scale from your tankless water heater every year -- some homeowners are somewhat skeptical of maintenance schedules published by contractors.
Mike,
Yeah, I suspect manuals act more as ways to cover yourself against claims by clients - and to Martins point may be (or be perceived to be) self-serving advice.
Given that, there may be implications as to what technologies we should include in houses. Spending time here on GBA it's easy to think of clients as interested in all this stuff, happy to constantly monitor sensors and controls, and actively maintaining equipment. That not generally being the case, choosing low-tech, low maintenance options may often be the best path.
The problem is that houses are built by builders, who are really in the business of selling houses rather than building them. And when you're selling a house the last thing you want to talk with the buyer about is maintenance, you want to be talking about barbecues and Thanksgiving dinners and all the fun and memories the house will bring. And the buyer doesn't want to hear about maintenance either.
I am a firm believer in water filtration and (where well wate is hard) softener. MY well produces water witha hardness of 193 mg/l (11 gpg). It also has iron and manganese. After the softener these are all close to zero. It would make sense to put i a softener or other filtration so that the water entering the tankless system is as close to pure as you can reasonably get.
Thanks for the guide. I did this to our exterior tankless after about 4 years of use with vinegar and concluded that it was unnecessary, I saw no change at all after recirculating for an hour. In my area the city reported water hardness ranges from 1.5-1.7 gpg or 29 mg/l. I'll do it again only if I notice any problem, but I expect the unit will die of something else before it's ever needed.
I read labels—carefully. Decades ago Lime Away was pretty good stuff and was largely composed of phosphoric acid (yeah, same stuff as in some soft drinks; sounds nasty but not terribly so). Nowadays it’s composed of a combination of organic acids and doesn’t work worth a damn. My plumbing supply sells descaling solution containing phosphoric acid and for a fairly steep price. One day, browsing my local restaurant supply store (The Restaurant Store) I discovered plastic bottles labeled for descaling ice machines and selling for relatively much less money.
Reading labels and SDSs can be a little tricky but is usually worthwhile. Producers are required to provide certain information about ingredients but they can often disguise the information in the form of CAS numbers (Chemical Abstract Services) which are very precise. It doesn’t provide concentration, though, and there are certain trade secrets that do not have to be divulged.
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