Should hot water tank be shut off when bleaching the water system?

[slackercruster]

Or does it do the hot water tank no harm?

 

Thanks

[D&J]

It shouldn't be running but it's one place that you want to sanitize because it's the first place thing will start to grow.

Denny

[Kirk W]

I agree with D&J. In addition, why waste the energy to heat water when you don't need to? The other thing that I suggest is that you turn off your water heater and drain the water from the system before you start the process. You will get a better sanitization if you start with the system dry. If you don't drain it first it will dilute your mix and make it more difficult to know that you get a complete sanitization of the system.  You do not want the the water heater operating when you drain it. 

Edited March 22, 2021 by Kirk W

[slackercruster]

OK thanks.

[LindaH]

23 hours ago, Kirk W said:

The other thing that I suggest is that you turn off your water heater and drain the water from the system before you start the process.

That's exactly what we did when we had "regular" water heaters (we now have a tankless water heater).  We'd drain the water heater, add the required amount of bleach to the fresh water tank, fill the water heater with the bleach water as well as run it through all the lines, and let it sit for a few hours or overnight.  Then we'd drain the water heater again as well as the fresh water tank, fill up the fresh water tank with water, fill up the water heater and run fresh water through all the lines.  At this point, some people use a second fresh water fill up using either vinegar or baking soda, but we never minded the small remaining bleach smell that remained and it quickly dissipated, so we never did a second rinse.

Of course, during all this the water heater is turned off -- you don't want it trying to heat water when the tank is empty!

[JimK]

For the first couple of years, when I sanitized the system, I put the tank on bypass.  Then one year the hot water just reeked to the point that it did not even feel safe to take a shower.  Now I always sanitize the entire HW system including the tank.

[Ray,IN]

Does bleach react with Aluminum? Short answer - YES. Long answer: https://perfectatom.com/does-bleach-react-with-aluminum-foil/

Dometic/Atwood water heaters have a pure aluminum inner liner.

 

Edited March 24, 2021 by Ray,IN

[Kirk W]

35 minutes ago, Ray,IN said:

Does bleach react with Aluminum? Short answer - YES. Long answer:

The tank in my Atwood water heater was sanitized annually with a mix if 1/4 cup chlorine bleach to every 15 gallons of water. (it would be interesting to know what % chlorine that is). That tank did fail in year 10 of fulltime use and year 11 of ownership. So was it due to the use of chlorine bleach? I'll leave that one to the experts. 

[JimK]

Household bleach is roughly 6-8% and the typical dilution of 1/4 cup to 15 gallons results in a 1:1000 dilution.  So 7 pph becomes 70 ppm.  For comparison typical chlorinated drinking water is roughly 4 ppm chlorine.  

It is true that chlorine bleach will corrode metals including stainless steel and aluminum.  The only study I saw was with bleach diluted 10 fold instead of 1000 fold.  Corrosion including staining and some pitting was noticeable after a couple of weeks.  Chlorine is also hard on many plastics but again  high concentrations are needed for long periods of time.

Although the concentrations used for sanitizing are very low some precautions are in order.  First don't add a lot more bleach thinking that more is better.  It is just harder on all of the water supply parts.  Second don't overdue soaking times.  I have looked and cannot find the original studies but years ago I researched this and found the recommended soak time for sanitizing was 1 hour.  The more is better idea seems to have taken over.  That somehow turned into several hours or even overnight.  Again an hour or two is totally sufficient.  The final issue is the frequency of sanitizing.  With regular use an RV water system seems to maintain purity indefinitely, certainly for many months.  Two factors can change that quickly.  The system has to be used and the old water replaced with fairly frequently with new, chlorinated city water.  Chlorine will dissipate over a period of a few days or certainly within a couple of weeks.  The second issue is removal of chlorine with water filters.  IMO, that is a very poor idea but if you google the topic you will find all sorts of positive ideas from the filter manufacturers.  The final problem is using untreated well or spring water.  Keeping the water flowing helps but with no chlorine contamination and growth of bacteria such as pseudomonas is just a matter of time and luck.  Contamination can be hard to detect.  Odors can arise for lots of reasons not bacterial growth.    

[Kirk W]

46 minutes ago, JimK said:

I have looked and cannot find the original studies but years ago I researched this and found the recommended soak time for sanitizing was 1 hour. 

I used to have the article that I got information from when developing my sanitizing process, but seem to have lost or misplaced it over the years. I am pretty sure that it said to allow the solution to stay in the system for at least 1 hour but not to exceed 2 hours.  I don't remember who the source was, other than it was from a university. 

The only time while on the road fulltime that we experienced algae problems we were using well water from a supply that was tested frequently but not chlorinated. That was in a KS state park and the main place it showed up was our white hose that was also exposed to direct sun. I have since read that keeping your hose out of direct sunlight will lower the probability of algae problems. 

[Ray,IN]

10 hours ago, Kirk W said:

I used to have the article that I got information from when developing my sanitizing process, but seem to have lost or misplaced it over the years. I am pretty sure that it said to allow the solution to stay in the system for at least 1 hour but not to exceed 2 hours.  I don't remember who the source was, other than it was from a university. 

The only time while on the road fulltime that we experienced algae problems we were using well water from a supply that was tested frequently but not chlorinated. That was in a KS state park and the main place it showed up was our white hose that was also exposed to direct sun. I have since read that keeping your hose out of direct sunlight will lower the probability of algae problems. 

Was it this CDC guideline paper?https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html

That's one of the sources I got the idea from of using Sodium Dichlor instead of regular bleach.

Edited March 26, 2021 by Ray,IN

[JimK]

I do not know if Kirk and I saw the same research paper, but this CDC paper was definitely not what I saw.  Nor does it apply to sanitizing an RV water tank.  The paper I remember was specific to RV water tanks.  Bottom line was 1/4 cup bleach to 15 gallons with a 1 hour soak.

[Kirk W]

7 hours ago, JimK said:

Bottom line was 1/4 cup bleach to 15 gallons with a 1 hour soak.

The same here and what I read was also about 20 years ago.