The standard amount is 1/4 cup of plain unscented household bleach for every 15 gallons of fresh water tank capacity.
That means:
| Fresh Water Tank Size | Bleach Amount |
|---|---|
| 15 gallons | 1/4 cup |
| 30 gallons | 1/2 cup |
| 45 gallons | 3/4 cup |
| 60 gallons | 1 cup |
| 75 gallons | 1 1/4 cups |
| 100 gallons | 1 2/3 cups |
Use this only for sanitizing the RV fresh water system, not for making a daily drinking-water mix. After sanitizing, the system must be drained and flushed with clean water.
Use the Right Type of Bleach
For RV fresh water tank sanitizing, use regular household bleach that is:
- Plain
- Unscented
- Liquid
- Not splashless
- Not gel
- Not color-safe
- Without added cleaners or fragrances
Do not use scented bleach, laundry additives, bathroom cleaner, or anything mixed with ammonia or other chemicals.
The goal is to sanitize the tank and plumbing, not leave chemical residue inside the system.
Why the Bleach Amount Matters
More bleach is not better.
Using too much can leave a strong smell, bad taste, and unnecessary chemical exposure inside your RV plumbing. It can also be hard on rubber seals, plastic parts, and fittings if the concentration is too strong or left too long.
Using too little may not sanitize the tank properly.
That is why the simple formula works well:
1/4 cup bleach per 15 gallons of tank capacity.
Step 1
Drain the Fresh Water System
Start by draining the fresh water tank.
Also open the low-point drains if your RV has them. Turn off the water pump before working on the system.
If you have a water filter, remove the cartridge before sanitizing. Bleach can damage filter media, and the filter can reduce the effectiveness of the sanitizing solution.
Step 2
Mix Bleach With Water First
Do not pour straight bleach directly into the fresh water inlet.
Mix the required bleach amount with water in a clean container first. A one-gallon jug works well.
Example:
If your RV has a 45-gallon fresh water tank, mix 3/4 cup of bleach into about one gallon of clean water.
Then add that diluted solution to the fresh water tank.
Step 3
Fill the Tank With Fresh Water
After adding the bleach solution, fill the tank with potable water.
The bleach needs to be diluted through the whole tank volume. Filling the tank also helps push the sanitizing solution through the plumbing lines.
Step 4
Run the Solution Through the Plumbing
Turn on the water pump.
Open each faucet one at a time until you smell chlorine, then close it.
Do this for:
- Kitchen faucet
- Bathroom sink
- Shower
- Toilet line
- Outdoor shower
- Any other water outlet
Run both hot and cold sides if you are sanitizing the whole plumbing system.
Check your RV manual for water heater instructions. Some owners include the water heater in the sanitizing process, while others bypass it during routine tank cleaning. If your water heater has special manufacturer instructions, follow them.
Step 5
Let It Sit
Let the bleach solution sit in the tank and lines long enough to sanitize the system.
A common practical range is 4 to 12 hours.
If the system is only lightly stale, several hours may be enough. If the RV has been stored for a long time or the water smells bad, leaving the solution overnight is usually more effective.
Do not leave a strong bleach solution sitting in the system for days.
Step 6
Drain and Flush Thoroughly
After the waiting period, drain the fresh water tank completely.
Then refill with clean potable water and run each faucet again until the bleach smell is gone.
You may need to flush more than once.
If the water still smells strongly of chlorine, drain and refill again.
How Often Should You Sanitize an RV Water Tank?
Most RV owners should sanitize the fresh water system:
- At the beginning of the travel season
- After long storage
- After buying a used RV
- If the water smells stale or musty
- After filling from a questionable water source
- Any time the system has been contaminated
If you use your RV often and always fill from clean potable sources, once or twice per year may be enough. If the RV sits for months, sanitize before using the water system again.
Signs Your RV Water Tank Needs Sanitizing
You should sanitize the system if you notice:
- Musty smell from faucets
- Strange taste
- Slimy feeling in the water line
- Stale water after storage
- Sediment or discoloration
- Unknown maintenance history
Do not ignore bad smell in an RV water system. It can come from old water, biofilm, contamination, or plumbing issues.
Can You Drink Water After Sanitizing?
Yes, but only after the system has been fully drained and flushed with clean water.
The final water should not have a strong bleach smell or chemical taste.
If you plan to drink from your RV tank regularly, use potable water sources, a clean drinking water hose, and proper filtration where needed.
Common Mistakes to Avoid
Avoid these mistakes when sanitizing your RV water tank:
- Using scented or splashless bleach
- Pouring undiluted bleach directly into fittings
- Forgetting to remove water filters
- Using too much bleach
- Not running the solution through all faucets
- Not flushing long enough after sanitizing
- Leaving old water sitting in the tank for months
- Filling with a dirty hose
A clean tank will not stay clean if the hose, filter housing, or fill connection is dirty.
Custom way Can Help With RV Water System Service
At Custom way, we help RV owners maintain, repair, and upgrade fresh water systems so they are safer, cleaner, and easier to use.
We can help with:
- RV fresh water tank sanitizing
- Water pump inspection
- Leak detection
- Plumbing line repair
- Water filter installation
- Faucet and shower upgrades
- Water heater inspection
- Full RV bathroom and plumbing renovation
If your RV water smells bad even after sanitizing, the problem may be deeper than old water in the tank. It can be connected to plumbing lines, filters, water heater issues, hidden leaks, or contaminated fittings.
Simple Formula to Remember
For most RV fresh water tanks, remember this:
Use 1/4 cup of plain unscented bleach per 15 gallons of tank capacity.
Mix it with water first, add it to the tank, fill with potable water, run it through the lines, let it sit, then drain and flush until the water is clean and the bleach smell is gone.
Done correctly, this simple maintenance step helps keep your RV water system fresh and ready for travel.