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RV Water Heater Flush & Inspection Surprise!

RV Water Heater Flush & Inspection Surprise!

Even though we’ve been on the road full-time for nearly 15 years, we never stop learning. Since it’s virtually impossible to know everything about every topic, the most valuable tool we keep on board is an open mind.

Last year we added a great new piece of (inexpensive) gear to our DIY utility belt: a borescope. Before that, we’d never been able to see inside our water heater to know what condition it was in, or to see what effect (if any) our annual cleaning regimen was having.

It turns out that a borescope is kind of like a clear sewer elbow for the water heater. We discovered a long time ago that we had no way of knowing what was happening during black tank flushing without a “window” into the sewer hose during the process. As a result, a clear elbow has been an indispensable part of properly managing our RV systems ever since.

Even though we had the epiphany to get a borescope to inspect the inside of the water heater last year, it wasn’t until this year, the second inspection, that we really “get it” when it comes to actually understanding what’s going on in there.

We were all set to do our annual flushing regimen, when the borescope threw us for a loop! Check out the video to see what happened, and what we learned.

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don hand

Wednesday 28th of November 2018

Thanks for your video. We have a 6 gallon Atwood heater. I wanted to use 4 gallons of vinegar to clean, but, the tank was full after about 3 3/4. That would have been ok, but it left vinegar in the line. I by passed the heater and my wife turned on the water and was not so happy with me for the vinegar smell. So next time, I will only use 3 gallons! Before I flushed, we were hearing the popping sound from the heater (we have owned the motorhome for 18 months). After draining the vinegar, a great deal of scale came out, and now we have a silent water heater again. Thanks again for the videos.


Thursday 29th of November 2018

Glad it all worked out and hope your lines are clear of vinegar now!

Michael (From South Africa)

Wednesday 22nd of August 2018

Hi guys,

I plan to flush my 4 gallon propane heated suburban Gyser with a 80 or 90/20 Vinegar mix concentration for the first time. The buildup of scale is bad as seen initially when I flushed it out by running water through. I wanted to ask you about the strength of vinegar choice you guys think is acceptable.

I contacted a bulk white vinegar supplier in my area (they supply to the hospitality trade) to find out what they can offer me. It turns out there are two options - 5% Vinegar and 10% vinegar concentrations.

Is it worth buying the stronger concentration? Its about double the price. Would a stronger concentration damage anything in my system?


The next question I wanted to ask is at what temp should I run my suburban propane heater on overnight? It shows three options, low, medium and hot.

Another question, do you think it is practical (in the case of my badly scaled heater/Gyser) to cycle the heater on and off a few times over a few days for better results? e.g 8 hours of heat then let it cool then another 8 hours of heat then let it cool etc ?


Last question relates to using food grade Citric Acid powder vs Vinegar and mixing that into a large water container and then using the winterizing kit to suck that into the heater gyser. What are your thoughts on Citric Acid vs Vinegar?

It seems like a cheaper alternative and from what I understand it is the same acid type as vinegar.

Thanks for taking the time for sharing your knowledge with us!




Wednesday 22nd of August 2018

Hi Michael!

First thing... from the sound of it, your water heater is different than what we're used to here in North America (4 gallon, multiple heat levels, etc), so we'd definitely recommend checking with the manufacturer first to be sure that using the vinegar/citric acid solution won't cause a problem and/or damage your water heater. If your tank is EXTREMELY coated with scale, we'd recommend a couple of different options: (1) let it "soak" for longer before draining, to give extra time for the reaction to occur, (2) purchase an inexpensive borescope like the one we used in this video to get a look inside the tank after treatment, to see if it needs a repeat, and (3) repeat the procedure if needed. If the scale is extremely bad, the acid in the vinegar will be consumed entirely in the reaction, so it may not completely remove it all. Repeating the procedure will ensure you get it all, without risking exposing the tank metals to too high an acid concentration.

Second... the white vinegar that we use in our water heater is a 3% solution. So when we fill our tank half full, it ends up being only 1.5%. We'd have some concern about ramping the concentration up too high... because the acid CAN begin to cause problems with the metals in the tank if it gets too strong. Again, not being familiar with your water heater unit in particular, we'd be afraid that there could be some components that would be adversely affected by too high a concentration.

Third... the chemical reaction between the acid in the vinegar and the lime scale in the tank is accelerated by heating it. So we're not sure that heating, then cooling, then heating would be any better than just heating it.

Last... we've heard from other viewers that they've used citric acid powder in lieu of white vinegar... since the powder is easier to store than gallons upon gallons of liquid. So that approach is certainly viable. It is NOT the same acid as what is in vinegar (acetic acid), but both are relatively mild acids and, at about the same concentration, should achieve the same results.

Hope this helps!


Tuesday 23rd of January 2018

Hi, Any reason the vinegar can't be poured into the water tank and then pumped into the hot water tank with the rv pump? I do this to pump RV antifreeze through my water lines when I winterize my RV. I realize I have to do a good job of rinsing the fresh water tank afterward.




Tuesday 23rd of January 2018

Hi Dan! As long as you get the vinegar into the water heater, that's all that really matters. Of course if you have a system that allows you to do it the way we do, without getting all that vinegar into the fresh water tank, it will save you a lot of flushing. In our case, our fresh water tank pickup line is a little above the bottom of the tank, which prevents us from draining all the water out. If yours is like that, the remaining water in the tank would dilute the vinegar enough that it might require more vinegar to maintain a good concentration. Of course if you've already used this technique successfully to winterize, and gotten a nice high concentration of anti-freeze through the system, it should be no problem in your case.

LESLIE Woodard

Friday 19th of January 2018

Hi I'm so addicted now to watching your videos. My husband watches your videos all the time. I have a question about how many gallons of vinegar to use in our 2008 travel supreme when flushing the water heater. I'm not sure how much to use. Could y'all help us out? Yall are awesome!


Friday 19th of January 2018

Hi Leslie! Thanks for the nice note. We generally about a 50-50 mix of vinegar & water, then leave it in overnight with the heater turned on. But as you saw in this video, a lot of that depends on the water conditions where we've been camping. Another factor will be the length of time it's been since you last flushed your heater out. Check out our previous video (here) to get a feel for our standard method. If will give you an idea of about how bad our tank was and how much debris came out of it, and how effective the time & vinegar concentration was.

We'd suggest that the first thing to do is to buy at least enough vinegar to fill your tank half way (5 gallons for a 10-gallon heater, etc). That way, you'll have at least that much on hand. If it's been several years since you flushed it and/or you've spent much time in the desert SW, you might consider getting enough vinegar to fill the whole tank. When you first remove the drain plug (on and Atwood), or the anode (on a Suburban), the amount of debris that comes out will give you a good idea how bad the tank is. If you get lots of chunks of white debris that continue to pour out, you probably have a LOT of scale in there. That would mean it's a good idea to either use a higher concentration of vinegar and/or leave it in longer. If you're living in it full-time, and it's a problem to be without hot water for very long, a higher concentration will allow you to leave it soaking for less time and still get the tank clean. If you're not living on board, and can let it soak for a couple of days, a lower concentration of vinegar should do okay.

If you really want to know what's happening in there, pick up an inexpensive borescope (we link to a good one for not much $ right here in the post), and inspect both before and after the vinegar treatment. Hope this helps!


Sunday 12th of November 2017

I've used my borescope to see behind panels and other hidden areas trying to find wires, lines or what do you suppose is in there, why didn't I think to look in the water heater? As usual, great video and great idea, I'm chagrined I didn't think of it myself when I serviced my water heater recently.


Monday 13th of November 2017

Hi Dave! We've done the same thing... using the borescope to see in all sorts of tight places. But we've forgotten we could do it a number of times, too. It's kind of like when you're in the store, see something you want to research more about later, and look for a piece of paper in your wallet to write it down... forgetting that you have a high-def camera in your smartphone and you could just snap a picture of it! LOL! A picture IS worth a 1,000 words! ;)

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