Tankless water heater clogged

[Mark Gibney]

Our Noritz tankless water heater seems to be clogged.
I usually flush it with vinegar annually but I'm getting lazier and I haven't done it in four years. The unit is about 12 years old.
This morning the hot water cut off while my wife was showering. This is a real life emergency!

I hooked up my pump to a bucket of vinegar and to the heater, as I do when I flush it, but nothing will pump through. The pump will whirl but nothing goes through the heater.

I cleaned the filter before trying to pump, and I've checked it since, and it's still clean.

I switched the hoses around so that the vinegar would be pumped in the reverse way, but still no joy.

I'm guessing that a bunch of scale broke off and clogged up the work well enough that I'm now stuck.

Have any of you any insights or experience with this problem?

I called Noritz and I'm waiting on a call back. Thanks.

[Mark Gibney]

Straight after posting the a Noritz tech called me back and recommended I use CLR diluted 1:1 with water, and to keep the pump working, not to worry that it will burn out.

I'll let you all know....

[Bruce King]

For others, because yours sounds worse. Unless you have what they call aggressive water the problem is usually just some gunk in the shower head. The quick fix is to run the hot water at the sink while in the shower to get the minimum flow required to ignite. Just buy a new shower head unless it’s just debris in the screen.
Did you prime your flush pump real good?

[Frank Pratt]

I think it's a long shot to get the scale out of those lines. Once plugged, it's pretty hard for the acid to migrate very far in the tubing. If you'd have caught it a day earlier...

[Mark Gibney]

You might be right Frank. I might be buying a new heater.

[Bill Dufour]

How much pressure does that pump put out? If less then city pressure fill it with acid then push it through with city water.
Bil lD

[Kev Williams]

The problem with such acids is that the calcium and scale you're trying to remove neutralizes the acid almost immediately. If you're totally plugged and trying to push acid thru, you'll soon have neutralized acid up against the blockage doing nothing... IMO you need to remove the whole heater so that you can pour in some fresh acid, wait a few seconds, pour it OUT, pour in more fresh, wait, pour it out, repeat... Wear gloves :) ... You don't need to pour in much, like 2 tablespoons at time. You'll know it's working because the reaction creates a lot of smoke and gas. Neutralized acid won't smoke. About every 4 acid treatments, flush with water a couple of times. Once you get thru the clog, then you can use a pump to circulate an acid mix thru to fully remove the remaining calcium and scale. Consider a fresh bucket of solution every few mintues. When done, mix a solution of baking soda and water to recirculate thru to neutralize any remaining acid. Then a fresh water flush, and you should be good as new...

Acid: I use muriatic acid diluted to 8%-ish on my boat hulls applied with a garden sprayer. I just spray about a square foot at a time- wait a few secs- spray, wait-- until the calcium's gone. Doesn't take long. Never had to use a brush ;) -I've been going to try 30% vinegar diluted to 15% but haven't yet. I use 6% cleaning vinegar around the house to remove deposits around the house, but it only seems half as strong (or less) than 8% muriatic. I DO know (the hard way) that 8% muriatic will darken some stainless steels, not sure about vinegar. Never used oxalic acid but it may be the safest.

[Frank Pratt]

I like Kev's idea. Lots of farting around, but if it save the price of a new heater, might be worth it.

[Mike Henderson]

Those tankless heaters have many small tubes that the water goes through. It's the only way the water can be heated that quickly as it passes through the heater.

If your problem is that the tubes are clogged, some of those tubes may stay clogged even after you get flow through the heater.

But having EVERY tube clogged such that nothing goes through the heater seems very unusual. If the tubes were clogging up, I would expect the flow to have decreased over time. Maybe there some single point of clog that you're dealing with.

Mike

[Bruce King]

Probably these corroded.

[Thomas McCurnin]

They actually make a designated product for the annual flushing of tankless heaters, not vinegar, and a couple of years ago introduced tankless water filters which prefilter the water with replaceable paper filters and a pressure gauge showing when the filter should be replaced. Noritz says it reduces the flushing frequency. I own a Noritz, flush every year using the Noritz recommended product, and installed the filter.

[Peter Kelly]

Do not use muriatic acid on your pipes ever, this can easily etch the inside of the copper coil of the tankless heater causing the lime scale to build up at an even faster rate as well create pinholes in copper pipes in random places. To unclog your tankless heater, add a 28 oz container of Lime-A-Way to 2 gallons of water and run the pump you've hooked up to the heater until it trips it's thermal switch a few times then let the solution sit in the coil for about 30 minutes. Reverse the pump direction so it's sucking and keep trying as the thermal switch will again trip a few times. This should free up the coils eventually. You'll also need to clean out the aerators on the ends of your faucets as well as any filters within the thermostatic valve in your shower. Should be back in business shortly. Lime-A-Way is a fairly strong nitric and citric acid mix so be careful handling it.

LA is known for very hard water so you may want to consider a softener and filtration system. Solves a lot of problems downstream.

[George Gibson]

I might be buying a new heater.
How much more will you use?
Now is the time to change.

[Jim Becker]

How much more will you use?
Now is the time to change.

Given the age of the unit, I'd likely opt for a replacement to a more efficient, current model from any of the several good manufacturers, especially since it sounds like it's pretty plugged up. Water conditioning can really help...we need acid neutralization here for our well water because it "eats" copper. Some water needs a lot more attention to deal with various risks.

[Thomas McCurnin]

My unit is over 15 years old, but we regularly flush it with the manufacturers recommended flushing solution and use the filter. The maintenance cost is less than $50 a year.

[Peter Kelly]

A decent quality tankless unit should last 20 years.

[Jim Becker]

A decent quality tankless unit should last 20 years.

Yes, they should but the water in certain areas makes thatgoal harder to obtain. We had similar longevity issues with tank type here, too. While the OP's issues are primarily water related, I'll also add that the circuitry in moden condensing water heaters can be susceptible to surge damage. I had that happen with one of our tankless units about a year ago. The replacement circuitry was 2/3 the cost of an entire new unit which was a no brainer on something that was already many years in service. (I have surge protection on both of them now to help with that, although a direct lightning hit would likely still take them and a whole bunch of other things out)