Tankless water heater - Vinegar flush

[justsam]

Conventional wisdom seems to be that these should be flushed with vinegar (white vinegar 5%) about every two years.

I have a granny unit on my property with a professionally installed Rinnai Integrity Model 2020, for an 800 Sq ft unit. All works fine and has for several years.

I would like to do a boiler flush on this unit however it was installed without isolation valves. It is easy enough for me to isolate the input, but no way for the output side. I can remove the PTV on the output side and get the bulk of the vinegar output from there but that would still leave the home hot water taps basically in parallel, which would mean dishwasher, washing machine, shower and sink faucets. They would be dead headed at the taps in the home.

Other than the taste/smell of vinegar for a period would there be harm to any of the seals in the various faucets? Plumbing is PEX and copper.

Or is the whole notion of a vinegar flush not even required?

 

[Jackfre]

2020? Haven't sold that in probably 12yrs anyway. Pick up a set of the iso valves and install them. Can you do that? Send me a pm with your address and I'll send you a set of them. The spec is 4 gal of white vinegar and let it run. DO NOT back flush. You will pump any debris back into the flow control valve.

 

[My Old Tools]

Yep, ran mine for an hour recirculating the vinegar. It was 10 years old and had never been done. You need those valves.

 

[justsam]

I did pull the cover off the unit to see if there was some way of isolating the output internally, (there was not!), and the manufacture date was 2003. The unit has never had an issue, however it does see light usage in what is mostly a guest cottage. The only failure was when the GFCI circuit providing control power to it failed. It was a defective GFCI, not the Rianni.

So it sounds like it is still wise to flush these out every couple years, and I do have a small sump pump and hoses.

 

[Bretny]

Installing a few pex valves is not even an hours job. I would put the valves in.

 

[justsam]

The unit is mounted on an outside wall, that sees a great deal of afternoon sun. Is PEX OK in a high UV environment? It is currently plumbed with copper and will use that if possible. Seems like a simple enough job, curious why the professional installer did not include them?

 

[Jackfre]

I think it was around 2005 that Rinnai began shipping all of the Luxury and Ultra series units with the valves in the box. The Value series has the same engine as the others, but doesn't have the recirc logic nor the valves in the box.

Got your pm. I'll get a set in the mail tomorrow

 

[justsam]

Jack,
Thank you for sharing your knowledge and for the valves.
Your time line makes sense as I have a larger Rinnai unit at my main house which was built after the guest house in 2006. It is a Continuum Model 2532 and indeed has the isolation valves making it very easy to do the vinegar flush. I also cleaned out the small input screen. The main house (4500 sq ft) also has a Grundfos circulation pump which I control via an Alexa command.

 

[Jackfre]

Just mailed the parts.

 

[Falcon67]

Side note - we put a big shot of vinegar in the dish washer periodically. Removes scale and can clean up glassware. Also use off the shelf white vinegar as the clothes rinse in the washer. Dont think it would take long to flush out the pipes anyway.

 

[BearsFan315]

i have a 5 gall bucket, set of hoses, and a cheap sum pump i use to flush mine, get a few gall of vinegar. set it up, connect it to the valves, flip em the right way, plug in pump and have a closed loop system and flush it per manual.

 

[Jackfre]

Also, pick up a fine mesh filter to catch any precipitant coming out of the unit. That way you can tell if there is any **** in there. It is all a water quality issue.