A clean freshwater system is very important in an RV. Seems like there's enough to make us sick these days without adding our own water system to the list!

While we're going to be focusing on our system, which uses the Nautilus P1, the process is very similar across all RVs. In the most basic of terms, its simply putting bleach water in the system, waiting 8-12 hours, then flushing it out. Let's get into more detail…

UPDATE! We had a few people reach out after the video with some advice on the Nautilus P1 system. It turns out the red knob bypasses the water heater even when in dry camping or shore water mode! This takes a few steps out of the process, making it much simpler for us Nautilus people.. ?

How Often?

How frequently you sanitize will really depend on the style of use. We've gone over 2 years without doing it or really needing it since our system is in use 365 days a year. Full-Timers will rarely need to sanitize as long as you use your freshwater tanks regularly (travel days, etc), and empty them when not in use (on shore water).

If you store your RV for a month or longer, the system should be sanitized prior to use. De-winterization is also a great time to sanitize.

We've had a few times when we've left water in the tanks too long and it starts to not smell so great. Dumping and flushing the tank takes care of it, but we decided it was time for us to do a full system sanitization. Also, we now empty our fresh tank as part of our camp set up.

Before You Sanitize

Before you start this process, you need to be on full hookups (with sewer). Additionally, you should ideally be on a city sewer system. Check with the RV Park or Campground to see if they are on city water/sewer and, if not, if it's okay to sanitize your tanks. Parks with smaller septic systems may not allow it.

Time your process to do the fill cycle in the afternoon, and the flush cycle the next morning for the least amount of “life” interruption.

What You Will Need

Unlike many projects, the items needed for this task are pretty simple:

  1. Bleach (One cup for every 50 gallons)
  2. Bucket (5 gallons preferably)
  3. Syphon Hose (or whatever delivery system your RV uses)
  4. Potable Water (to use while your water system is in lock-down)
  5. Painters Tape (or similar – to mark your faucets so you don't try to use them)

That's it! The thing that will vary from RV to RV is the delivery system (how you will get bleach water into your tank(s) and lines. For this, you will need to consult your RV's manual.

Water Heater Bypass

Before you sanitize your water system, you will need to bypass your water heater. Bleach is very caustic to metal and the water heater is made of metal.

The method for doing this will also vary from RV to RV. However, many RV's use the standard H-Shaped bypass system whereby you close the lines into and out of the water heater and open the bypass valve (see video).

Our Nautilus P1 system automatically bypasses the water heater in winterize and sanitize mode, so we can skip this step. But, we will use a bypass trick below.


The goal here is to get a 1 cup of bleach per 50 gallons or water mixture into the fresh tanks and all of the lines to the sinks and showers (and washer if so equipped). Again, this process will vary from RV to RV, so check your owners manual.

For the Nautilus P1 system, it's a simple matter of turning the knobs to the right positions. The labels, however, can be a bit confusing. Ignore the “title” of the setting (winterize / sanitize) and go by the descriptions:

Fresh Water Tank(s)

For us, the first step is to fill the fresh tanks with bleach solution. It helps to already have them about 80% full before starting.
“Syphon to Tank” does just what it says. Fill your bucket with the bleach-water solution, keeping in mind that the amount of bleach is for the entire fresh tank capacity. We have 150 gallons of fresh tank capacity, so the point is to introduce 3 cups of bleach. What mixture you use is up to you. We decided to use 3 buckets with 1 cup each, but 3 cups into one bucket is fine also.

Attach the siphon hose, place the nautilus dials into “sanitize / siphon to tank” mode, and turn on the pump. Repeat this process to get the appropriate amount of bleach into the fresh tank.

No need to top off the tanks yet, we'll get to that later.

Fresh Water Lines

This is the part that was made much simpler thanks to our awesome viewers!

Put the system in Dry Camping Mode (water is supplied from the tanks), but turn the RED valve to the left to bypass the water heater.

Turn on the pump and run each cold and hot faucet, shower, etc (separately) till you smell bleach. If you have a washing machine, run a small empty warm cycle (be sure to let it finish the cycle and drain). If you have a residential fridge with an ice maker, let a couple of cycles of ice run through (put the ice in your sink – do not use).

Top off the fresh tanks till full (over-flow) (only if you have an over-flow mechanism that drains under the RV).

Put some blue painters tape (or some kind of reminder) on all faucets so you don't forget to not run the water.

That's it for the first half of the process… Wait 8-12 hours…


Now comes the easy but long part of the process (depending on your fresh tank size).

Put the Nautilus system (or whatever your system is) into dry camping mode (except the RED valve – turn that LEFT), turn on the pump, and open a COLD fixture, and open the grey dump valve for that fixture.

Run the cold water until the fresh tank is empty. Fill the fresh tank with clean water using the power-fill mode, then empty it again (same process as above).

The fresh tank is now empty and free of bleach.

Power-Fill the fresh tank with enough water to flush your fixture lines plus a little extra so you don't run the pump dry. We used about 25 gallons.

While still in dry camp mode (and RED Left – water heater bypassed), run each fixture hot and cold to purge the bleach water from the lines. Run them till you smell no bleach, then run them for another minute to get a good flush. If you have a washer, run another warm cycle to purge those lines also.

Set the system back to shore water mode, then dump all water from the fresh tanks. Use discretion when doing this. Water dumping under the RV can draw some critical eyes from RV Park Lookie-loos. ? You can use your water pump in dry camp mode to empty the fresh tank 99% then use the dump valves if you are concerned about dumping too much freshwater.

Leave the fresh tank empty till the next time you will use it. An empty tank will not breed microbes like one with water in it. Remember to put the RED valve back to the normal (UP) setting.

Congratulations! You now have a (mostly) germ-free fresh water system! ?


? RV Maintenance Series (PlayList): www.youtube.com… 
? RV Water Management: youtu.be/bR7e7XViI3o… 

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