Tankless Water Heater DeScaling - How To Flush 

One thing you should look into to doing. I am a plumber and do this alot by the way. I use a inline filter on the outlet line to catch all the sediment to keep from putting back into the unit. A sock and a couple rubber bands or hose clamps at the end of the hose works well too. It also shows you how much debris you really pull out of it.

This was an exact replacement for the old one that lasted about 10 years. ru-vid.comUgkx7yWIKcrbA9KMHkGSfcgxW2lsjHT6B8Sh The top of my mitigation tube by my roofline was just a 90 elbow which allowed too much debris to fall down into the fan, eventually ruining it. Without this issue, I bet it would have kept running another 10 years. When I replaced this fan, I added an extra elbow joint so the top tube now it does a 180, which should solve that problem. The radon guys around here wanted to charge me a $300 diagnostic fee, then parts/labor (probably close to $600 total). I installed this all by myself in about an hour for the cost of the fan; it would probably be even easier/faster with two people. FYI the manufacturer's warranty greatly differs depending on whether you install it yourself (1 yr warranty) or have a licensed installer do it (10 yrs).

I watch this video once a year and I appreciate it every time.

This has been my go to "how to" video. Have done it for at least 5 times so far.

I've had this tankless system for yrs, NO ONE, told me this might be why I'm having hot water issues. Gonna give this a try, and thank you, whoever said to use a swamp cooler pump.

this work prefectly...thanks for saving me almost $300 ... after you stated that your hose was rusty. I decided to fill the bucket with clear water and sit the pump back in the bucket and run through the hose...just to clear out that vinegar....but again, this is a great video...well done!

I've watched a ton of these for my tankless video. This is by far the best for someone who is a layman. Your videos are straightforward and easy to understand. Because of your video, I completed my tankless flush with zero mistakes. I purchased a Tankless Water Flush kit from Home Depot which includes the 5GAL bucket, hoses, and the pump.

Your videos are literally the best! The one on heat tape just saved me from the Texas Winterpocalypse.

Matt, thank you so much for providing this cost-saving, detailed, easy to follow video. I've followed your step by step process now for several years and it's given me the confidence to try other projects around the house, as well as save money on water heater maintenance every year. This is fantastic!

Thanks Matt! This is one of the best DIY video I've come across. Why? Because, you kept it simple and focused, you spoke clearly and unrushed, you demonstrated the steps and what each step accomplishes, and finally you explained why doing this regularly is important. I'm going to subscribe to see what else I can learn. Mahalo!

Thank you! This was a great step-by-step how-to - I picked up a pump, 5 gallon bucket, and hoses, and it took only a few minutes to get my Rinnai cleaning under way! I did have a good bit of trouble getting the small cylindrical filter out (maybe a sign that I was due for a cleaning!), otherwise so easy to follow. I did find I needed to power off the remote display, as it started beeping when I started the process. I let the pump run a couple of hours - next cleaning I'll adhere to the 60-90 minute cleaning cycle, as the vinegar was dark and hot by the time I was done. I paid the plumber who'd installed it a few years ago $125 or so when he came out a couple of years ago to do a flush service, and he teased that I really should be doing it myself and saving over $100 - while the set-up cost me that much this year, now that I know how, $8 in vinegar will make for great savings next year... Thanks again!!

great vid, I called local plummer/hvac company as we have been in our home for exactly 1 year and this is standard to do annually, he wanted 275.00 to perform this cleaning. I was going to have someone do a PM on the A/C and Tankless water heater but it just seems crazy this is what people want for a simple exercise. I appreciate the good quality video and detailed steps.

I had the same tankless water heater installed 10 years ago and I never knew i had to clean it.Im getting the items together now and will clean it this weekend.Thank you for showing me what an easy job this is to do.

Matt, thank you for the simple explanation. First year in new home that came with Takagi tankless so this was my first attempt at descaling. Went very smooth. After reading differing opinions on whether this should be done or not I called manufacturer and they confirmed all Takagi models need this descaling. Thanks again!

I come back to this video every spring. It’s easy to understand. Thank you.

Completing your steps as I write this. All looks to be going perfect. I am doing a house with a water softener and this is a 1st time flush after the Rinnai has been installed for 2 years. The filter was pristine on removal. Tks for a great training tool!

Thank you so much for the vid. I'm in Texas and also have a Rinnai. Vid saved me $ not needing someone to come out to do it.

Great comment to check the filter; none of the other videos pointed out this item to check. Note, if you check the filter, there is an O-ring that may have to be replaced.

2020: just did my house and my moms house. Thank you! This video is forever saved in my archive!

Matt, Thanks for the terrifically helpful video. Vinegar is circulating through my Rennai TWH as I type this. You have a real gift for communicating clearly and confidently, a real blessing to jittery DIYers tackling this for the first time. I was a bit concerned when the unit started beeping a me - temperature warning - but just figured I should turn the On/Off switch to off, even though I left the power hooked up as you said. Thanks again, Matt. Best of success to you! Rod Schwartz Pullman, WA

I watch this video every six months. Thanks for the easy to follow instructions.

Matt thank you for your easy to understand video, the Rinnai system you showed is just like my installation, I would add to your instructions to turn off the electric to the tank, it will beep for an hour and a half, one other point here in Raleigh, North Carolina the temps got down to six above last winter, I had to insulate my two water valves. Again thank you Matt you did a great video. John A Sullivan Raleigh, North Carolina.

Thank you Matt Risinger! I watched your video 3 times and paused many to go step by step with you...I am so proud to be able to do this myself...you took any fear away that I had about doing this myself...

As a Rinnai trainer, and a former Noritz trainer, I would like to note that if you don't have hard water, (not everybody does) or run the unit at high temperatures (above 120*F), you may actually do more harm than good. If there is no scale in the unit and you flush with vinegar for up to an hour and half it won't have any scale to "eat" and can deteriorate the copper heat exchanger. (not called a boiler, the terms get mixed up all the time) Also the Rinnai unit has the ablity to let you know when it requires flushing with the "LC" error code, minimizing the importance of anual flushing for the average home. Of course if you know you have hard water, you should service the unit reguarly as noted here. Also, the pump should be capable of flowing about 3GPM or more through the unit to do a good cleaning. As a test, mine are 7 years old, on very hard well water. Never flushed, never had trouble. Probably will flush soon just to see what comes out. Good job on the video! Google my Tankless 101 series for even more info on these great products!

You are worth gold! In the co-op housing unit we lived in we had an extremely expensive several thousand dollar instantaneous hot water heater. After 7 years of not being descaled we had to buy a whole new instantaneous hot water heater. A couple of bottles of white vinegar and the right fittings would have been much cheaper than paying another 8 to $12,000 for another unit.

Thanks Matt, great video you solved the question as where and what circulating pump is needed to preform this task! I have to say Rinnai completely drops the ball when it comes to flushing these units! I might as well have been speaking a foreign language when I asked their customer service where I could get a circulating pump to flush my unit!

Very glad to help! Appreciate your kind words. Best, Matt

Thanks for the video Matt. I appreciate the refresher course. I like that you didn't edit out the "things that happen" like the hose failure as such...Folks-"Stuff happens" and that is the reality of any fix it project. Our well water will leave white scale residue on a clear glass, so this is a great remedy for our tankless. Thanks again!

Thank you for this very helpful video. I was able to do this with the parts you recommended and a few gallons of white vinegar. Only took about 1.5 hours including setup and cleanup and saved me several hundred dollars. Some other folks in our community are following your instructions as well. Thanks for taking the time to put this together.

Man I've paid the last 2 years for someone to do this for me. I heard the process was easy, but I didn't know it was this easy. I'll try to knock this out this weekend. I have that same tankless unit and I'm in Austin so it's like this video was made for me!

"60 minutes to an hour" - priceless! :D Good you've corrected yourself immediately. :) I like the video. It explains a lot. I was just wondering how that kind of flush is done. I wouldn't like to miss some step while doing it. And here I found your video. It's a nicely done one and educative. I like to learn new things like that. Congrats on your teaching skills. :) Have a nice day.

wow. glad I ran across this video. I built a new house in '16 for my family of 9 that has 2 tankless heaters in it, no one ever told me I need to do this. Ill get to it. Thanks for the video!

The Rinnai manual also recommends that you rinse the cleaning solution from the water heater as follows: a. remove the free end of the drain hose from the pail b. close cold water service valve and open cold water shutoff valve. Do not open hot water shutoff valve. c. allow water to flow through the water heater for 5 minutes It appears that you must run the drain hose outside to rinse the tank; otherwise, you will have a lot of water flowing where ever you have your drain hose.

I have the Rinnai RL75 two years old. Just finished its first flush with your method worked great except I put an old sock held on with a coupe of rubber bands over the return hose to keep from pumping junk back thru the tank. Plus I unplugged the unit after turning the gas off so I wouldn't get error code 11.

I bought a near new high-dollar tankless for cheap. Homeowner hated the wait time for warm water in her 2nd floor bath, so i put back a 50-gallon/circulation system. Yes she was told tankless was very efficient & the best? She had to wake up turn on lav faucet, go to the kitchen, make coffee & back upstairs,,,maybe by then (warm-wash-water)? Thankx Matt!

Project completed. Thank you. It is important to check the prefilter before you turn the water back on.

would have been nice to have a visual on what your setup looked like with your sump pump and your buckets. you're very articulate, but that would have completed the clarity you seemed to present.

When you doing maintenence for any tankless water heater, combi, hybrid etc. While you runing your vinegar you need to inspect burner assembly, heat exchenger, condition of ignitor and flame rod, fan blower wheel, and clean them if need, also im recomend first to run vinegar then inspect inline strainer( for rinnai specificlly) if your water hard enough you wil brake that plastic. Also needle nose pliers is only tool to open inline water strainer. Regards Greg.

Thanks for your video Matt. I did call Rinnai and i was suggested to keep the gas line on. Turn on hot water and when getting a stream of hot water, unplug the unit. This will keep the valves open. Use vinegar for 45 minutes, as it's effectiveness is pretty much gone after 45 min. Maybe use 3 gallons for 45 min and another 2 for 45 more minutes. This is for my model # of RUC98i. Different units may have slightly different directions. Another suggestion is to put a cloth such as panty hose or similar over the sump pump which will keep the scale from going back into the heater Thanks for your video, doing this was a breeze.

Thanks Ryan! Appreciate your kind words. Best, Matt

Dont forget to flush that vinegar out of the tank as well. After cleaning we open cold side but not the hot side for 10 minutes to get the chemicals out before opening hot water valve.

Love the way those valves turn with finger pressure. I had to use a wrench and a hammer. They closed way easier than they opened. May have cleared a little crust. Much thanks for the very clear instructions.

Every year or so, I come to this video right before I flush my tank less... Thank you so much!

I stretched mine to almost 3 years. Very glad I watched your video, I totally forgot about the pre-filter, which was clogged. Thanks from Chicago!

This is the most helpful video after viewing multiple videos. I could see all the connections, parts, pieces, and way to proceed in a sequential order. Thank you, Matt. My neighbors who have tankless water heaters have asked me to descale theirs. A new career after retiring from teaching high school English.

Worked great but I had to double up the washers to stop it from leaking on the intake. I had an estimate from a local plumber to do this for $400 (can I say rip off?). I spent less than $80 bucks, and can do it yearly, or so now. Thanks Matt for this video it was pretty easy!!

Super comprehensive description of what needs to be done I really enjoyed doing this process it was interesting because the dinner eager afternoon I have had a slightly aqua blue look to it

Thanks for the video. Just got a Rinnai installed yesterday. In San Antonio, so we have hard water as well. Again, thanks!

Thank you Matt for your FABULOUS videos. I am so impressed with your extensive knowledge and how great you are to share these helpful videos.

I re watch this video every year and it’s my favorite thing in the world thank you

Got a nice color change using 3gal and a cheap pond pump from harbor freight $27 piece of cake and seems to work great, it's the chemical that cleans not the pressure so it just needs circulation

Just did mine !!!!!!! Wow !!!!!!!!! Brass never looked so clean !!!!!! Thanks for the video !!!

These can be mounted outside in cold climates, but I probably wouldn't. They have an internal heater that works to keep the boiler from freezing down to about Zero degrees. However, if the power goes out you are in trouble. Mount it inside your garage or basement if you live in the North. In Texas or the South you can easily mount this outside. Best, Matt Risinger

Great article as I didn't realize that my system needed to be cleaned and frequency. Although I have soft water I will still do this, after 5 years of 2 person use and then maybe ever year or so unless residue is no longer a problem.

Great instructional video. I went to Home Depot and made my own DIY kit with a 5 gal bucket, pump, and hoses. definitely easier than I thought to do and saves a couple hundred bucks plumbers want to charge to do a flush.

I did it! I ordered the parts; got them delivered, and BAM! Thank you!

Thank you SOOOOO much! This was all so confusing to me because none of the other videos looked like the set up I have and I couldn't even figure out how to turn off the water. Yours looks exactly like mine, and the instructions were clear, so I have successfully done this and am so grateful. Thank you!

If you have a newer Noritz, make sure to connect the "Flush Wire". If you don't connect the "Flush Wire" it won't reset your code and you'll have wasted time. We learned this the hard way. Had a code 21, didn't know about the flush wire, flushed the system, but the code stayed and the system wouldn't work. You have to connect the "Flush Wire" for a Noritz. We connected it and flushed it again and it worked.

I had some schooling on these water heaters they are awesome we own one for proximately nine years thank you for your important maintenance video.

when you do have problems with these units, it's amazing no plumbers know how to work on them. They just want to install new units

I did stop and emptied the vinegar and then flushed with water to clear the tank and pump of vinegar. Looks great now. We have a lot of iron here in north Florida so I think that's the reason for discoloration. I ended up flushing a total of 50 minutes. Thanks this will save us a lot of money over the coming years.

This video didn't exist before I installed my Navien ten years ago. I wished it would have, because I would have had the clean out valves installed. Unfortunately I didn't think about maintenance being required - that is a perfect solution.

Great presentation in a professional level.

Never knew to do this until my brother mentioned it. Great explanation! Thanks Matt!

I would mention that the nearest hot water faucet to the unit should be opened before the gas (or power) is turned back on to get rid of air pockets in the unit. An electric tankless water heater will fry the elements if there is no water inside the unit.

Thanks a ton for posting this Matt. I've been wanting to do this myself since we got our tankless installed and this was the perfect push to do so. As usual, awesome video.

Timothy Huang, There is no pilot light on these units. They have electronic ignition so they only light the gas when there is a call for hot water. Nothing to re-light. Best, Matt

This was the video that got me started watching all your videos and the world of building science.

I can vouch from a bad experience the need to do this process regularly. I let mine go over 4 years between flushes and my unit stopped working. It ended up costing me a thousand bucks to have a new sensor installed because the original one got fouled up from lack of flushing. Not to mention the embarrassment of being lectured by the plumber who thought I was really stupid for letting it go that long (I was). . .

These were good instructions, but one thing that is missing is that you should flush out the tank with water through the hot side after you're done with the vinegar. He mentioned this in his newer video on this topic but for some reason did not include it here. After I flushed the vinegar today for 90 minutes, the vinegar turned a bluish hue, but when I then followed up with clean water from the street that I discarded through the hot side, it was gray and murky. Glad I did that.

Thank you for this video. I will make a donation. (1) Find and use a hose kit with plastic connectors. The vinegar reacted with the brass connectors in my hose kit. The in-line filter caught the flakes of reacted metal from the connectors, so it was really not an issue. (2) The Rinnai manual indicates to rinse the vinegar from the water heater by not opening the hot water shut-off valve, retaining the drain hose from the hot water line, and running water through the system for five minutes.

Thanks, I watched you a year ago............wanted to refresh my memory.

Thanks for the video! (You call both the bucket and the pump the "tank" and the hose connector a "valve")

Great instructional video. I followed exact steps on my Rinnai heater and it worked perfectly. Thanks!

Great Video, thanks for making it. I'd add a good flush with cold water from the cold side is a good idea before closing up the hot side and returning all the valves back to the operational positions.

As always Matt, very clear and concise how to video. Love these. Please keep doing what you are doing. Thumbs Up!

Thanks for this video Matt. Always fun when I randomly come across a video and they mention our home town! My plumber wanted $250 to flush mine. I said no thanks and I've been meaning to find a video to show me how to do this.

I would have liked what the bucket, pump and hoses look when you are all hooked up and ready to start the pump.

Great quality video Matt. I am hear just to learn as I don't have any experience and don't have tankless.

You've come so far! I just missed the "Let's get started" tag line...

Strange, this worked like a charm 1st time (RL75). Matt describes perfectly. Now (2 years later) nothing's flowing through. Filter was clean. I saw some weird "Fixes" on another site (reverse flow or having water heater on for 30 secs at the beginning - I'm too scared to try). Once I switch back to the isolation valves, everything is fine again It's almost like the drain valve is blocked inside. I tested my 1/5 hp submersion pump - seems to run strong.

Thank you! Also, thank you Dillan Waters! You guys just saved me hundreds of dollars!

Thank you for this video. Short, clear and easy to understand.

Straightforward and easy to understand video. I feel confident in tackling this myself. Thank you so much good sir 👍

Thank you..! I am doing this right now.. I was lucky to have stumbled across this video because.. You and I have the same brand water heater.. And set up was seamless..!

Great vid. I'm cleaning my tankless water heater now. I hope you got a new hose. Thanks for the vid.

This was very helpful video. I have hard water and a lot of sediment got pumped out of my Rinnai

No big deal, shouldn't be a problem at all. Matt

After you're done, let the end hoses (the ones rusted) sit on the vinegar so those get clean up as well! then just put some baking soda after your done so the reaction to vinegar stops... it will extend the life of your hoses...

@dennisv21 Nothing you need to do with your reducer valve. The flushing is only inside your unit. Best, Matt

At first I read the Rinnai manual, and it was no help, too technical to get. I watched the offical Rinnai video here on youtube.com on flushing these tankless water heaters, and they told me "not" to use a pump that exceeds 5 (gpm) gallons per minute. I found a 4.4 gpm pump and called my plumber and was told to run it for 1.5 hours since I was a little below 5 gpm. I already had a 1/2 hp sump pump that ran at like 13,000 gpm and was told to "no way" use it as it was too powerful. This has been a totally new experience for me, and I sure don't want to damage any sensors internally. I suggest you call Rinnai on their 800 # if you have questions about the pump output, it's better to look before we leap.

Thank you so much for the video sir. Just taught me something new to help me with maintenance

If you do these often you will need a corrosion proof pump. It will cost you a few bucks but is necessary. Standard submersible pumps or water heater transfer pumps will get ruined pretty quickly by the vinegar. No one ever mentions this but it is true.

Matt's one of the best out there. Nice job!

I told the homeowner "I don't service tankless heaters, I install them". Also, told him to just leave it "as is" cuz it's still working fine. Once I touch it I'm married to it. He talked me into flushing it with vinegar anyway.....said if something went bad he wouldn't hold me to it.. No pump so I took a brand new Hudson Sprayer, put a couple pints of vinegar in, hooked it up to the cold water inlet, filled the unit and shut the valves to let it set for an hour. Came back and it was leaking INSIDE THE HOUSING. Something about pure vinegar did a number on a couple small O-ring joints, where the water enters and exits the heat exchanger. Ended up hanging a brand new one ( $1,400.00 and change). Good thing we had the talk before. I can hear another customer saying "Well...it wasn't leaking before you touched it". Never again for me. I'd rather have my customers mad at somebody else than me.

Awesome little video, sir! Plus the links to all the necessary goodies ... top notch!

I greatly thank you for the walkthrough, I appreciate the effort and time you put into helping others.

Lochinvar combi boiler is superior to the cheap Rinnai , also red valve is Hot Matt ! Good video .

You might want to change your pump rec. The link you have now costs $122. A similar 1/6 hp water heater kit from superior pump costs the same on Amazon, but the Superior pump by itself is about $75. The 1/4 hp Superior pump that is otherwise identical is $55. My apologies if this is repetitive, but there's way too many posts to read through.

Wow Matt, watching these old videos.... You aged well!