Sanitizing the Fresh Water Tank(s)

We already have three articles on dewinterizing and sanitizing, but I get a lot of questions specifically about sanitizing the fresh water tank(s) and I thought that having an article just on this would be helpful. I will repeat the steps here but read the whole article before you follow these steps -

1. TURN HOT WATER BYPASS VALVES TO HOT WATER FLOW.
2.  USE CITY WATER LINE TO FILL HOT WATER TANK BY RUNNING CITY WATER INTO THAT TANK. (NOT CITY WATER FILL - REGULAR USE OF CITY WATER)
3. DISCONNECT CITY WATER CONNECT FROM HOSE.
4. *PUT ONE HALF CUP BLEACH INTO THE FRONT EXTERIOR FRESH TANK. (PRE-MIX THE BLEACH IN A GALLON JUG OF WATER BEFORE PUTTING IT INTO THE FRESH TANK - DO NOT PUT PURE BLEACH INTO THE TANK.)
5. *PUT ONE QUARTER CUP BLEACH INTO THE REAR INTERIOR FRESH TANK. (PRE-MIX THE BLEACH IN A GALLON JUG OF WATER BEFORE PUTTING IT INTO THE FRESH TANK - DO NOT PUT PURE BLEACH INTO THE TANK.)
6. TOP OFF WATER IN TANKS WITH HOSE.
7. DRIVE BACK AND FORTH TO MIX THE BLEACH INTO THE WATER.
8. TURN ON BATTERY SWITCH AND WATER PUMP.
9. **TURN ON EACH FAUCET HANDLE PLUS INSIDE AND OUTSIDE SHOWER ONE HANDLE AT A TIME SMELLING FOR BLEACH TO COME THROUGH WITH EACH. NOT THE TOILET.
10. LET BLEACH SIT IN TANKS FOR AT LEAST FOUR HOURS.
11. DRAIN WATER TANKS.
12. FILL WATER TANKS AGAIN.
13. **REPEAT STEP 9 SMELLING NOW FOR NO BLEACH SMELL.
14. DRAIN TANKS THROUGH THE LOW POINT DRAIN.
15. REPEAT STEP 9. IF BLEACH SMELL AGAIN REPEAT FROM STEP 12.
16. DRAIN TANKS OR LEAVE FULL FOR TRIP

* IF you have a single fresh water tank (which is the capacity of the two tanks combined, use 3/4 cup of bleach for the one tank. - Mix it with water first. 

If you have seen our step by step de-winterizing and sanitizing article you will note that Step 4 has been changed. Do not put pure bleach down into the tank. Mix it with water first by pouring the bleach into a gallon jug with a little less than a gallon of water - to have room for the bleach in the jug. There is a lot of discussion on various RV forums about just how much bleach to use. Some say a quarter cup, some say a half cup - as I have here, and some talk about a full cup of bleach or more. Fresh tanks vary in size from type of RV to RV. The Roadtrek has smaller fresh water tanks than most RVs and you really want to take that into consideration when you prepare your bleach mixture for sanitizing. With a 190 or 210 and their two fresh water tanks you are going to be putting the bleach/water mixture into each tank. It occurred to me this year when sanitizing that perhaps too much bleach was going into the interior, rear, smaller fresh tank. I cut that down to 1/4 cup of bleach. Some of the bleach is going to flow into the hot water heater when you open the hot water faucet - and you will be adding some bleach into that tank in this manner. See the asterisk just above for single tank systems.

Make sure you use a recent bottle of bleach. We had a bottle of bleach that was not past the expiration date stamped on the bottle but when I poured the bleach into the jug of water there was no strong smell of bleach. It was faint at best. I did what my chem professor instructed so long ago and put my nose not over but near the open bottle and waved my hand toward my nose over the top of the bottle - no strong bleach odor. This resulted in a quick trip to the supermarket for a new bottle of bleach and this one could be smelled as soon as the bottle was opened and it was strong in the water as well. You will waste all of your time and efforts with an old bottle of bleach.

Everything else is pretty straight forward as always with just one more exception. See that double asterisk ** on Steps 9 and 13. While I was doing these steps this year I realized that everything smelled of bleach at the sink. The water seemed to smell of bleach as it came out of the faucet but when it was off I still smelled bleach. That is because the bleach water was now in the sink and the sink smelled of bleach. So - get a paper cup - any size - and when you open the faucets and the showers to smell bleach, run the bleach water into the cup - just an inch will do. Smell what is in the cup. This way you know it is the water from the tanks and plumbing that you are smelling. I flushed the tanks twice and I thought I still smelled bleach - but it was not coming from the water now - it was coming from the sink with the bleach water that had run into it before.

Can it sit for more than four hours? Yes, it can. Some say to let it sit for 24 hours. Bleach mixed with water in these proportions will dissipate after about four hours.What you are left with is water with a bleach smell and no potent bleach. The bleach's work is done in four hours. If you run out of time and it has to sit until the next day - no problem!

The sanitizing process is the most time consuming of the de-winterizing process. And it is only because it takes time to fill the tanks, wait the time for the bleach to work, and then flush the tanks - and flush again if needed.

Do you need to do this more than once a year? If you use your RV 12 months a year, you may want to do this twice or even three times a year. If you let your RV sit a long time - months (not weeks or one month) between trips you might want to do this again before you use the RV again.What you are doing is killing any mold or bacteria that may have developed and grown inside your fresh water tank.

Now - every year that we have sanitized the tanks after de-winterizing we have experienced the same problem with the second tank - the rear interior tank. When we try to refill the tank after draining the bleach and water out of it, water starts to go in and then when the tank sensor shows one third (which can be anything from a quart of water to actually one third full) the water backs up the fill hole and pours out - with no more water going into the tank. This does not happen with the front exterior tank at all - just the rear tank. We have dealt with this in different ways each year. Last year I created a tool to deal with this and I will tell you all about that tool, or perhaps it is more a gizmo, with photos in our next article.