A lot of rigs are coming out of summer storage right now. Sanitizing the fresh water system is the maintenance item that gets skipped most often, and it's the one most likely to ruin a first trip out.

Water sitting in a tank and plumbing lines for weeks or months develops odor and creates conditions where bacteria and biofilm can grow. The fix takes household supplies and about half a day, most of which is waiting.

Owner's manuals vary a lot here — plumbing layouts, water heater bypasses, filtration setups, and water management panels are all manufacturer-specific. Worth checking yours before starting.

When sanitizing is recommended

• Start of camping season
• After dewinterizing
• Before or after long-term storage
• After buying a used RV
• Any time the water tastes or smells off
• After filling from a questionable water source

Signs the system is overdue

• Stale, musty, or sulfur smell at the faucets
• Off taste in the water
• Cloudy water after the rig has been sitting
• Tank that wasn't fully drained before storage

Most people notice it the first time they turn on a faucet after storage. If the water doesn't smell right, sanitizing is usually the first thing to rule out before chasing other causes.

Step 1 — Drain the old water

Empty the fresh tank completely using the tank drain, which is either a line under the coach or a valve in the wet bay depending on the build.

Then open all faucets and both low-point drains. Most rigs have separate hot and cold low points, and both need to be open to clear the lines.

Close everything back up once it's drained.

Step 2 — Pull the filters

Check manufacturer guidance first, but most owners remove filter cartridges before introducing chlorine. It protects the filter media and lets the solution circulate through the plumbing instead of getting caught in the filter.

That includes inline filters, canister filters, refrigerator filters, and any whole-coach filtration system.

Step 3 — Mix the solution

One quarter cup of unscented household bleach per 15 gallons of fresh tank capacity.

• 15 gal → 1/4 cup
• 30 gal → 1/2 cup
• 45 gal → 3/4 cup
• 60 gal → 1 cup
• 75 gal → 1 1/4 cups

Use plain unscented bleach intended for disinfection only. No scented versions, no splashless formulas, no gels, nothing with added cleaners in it. And never combine bleach with any other cleaning product.

Pre-dilute the bleach in a gallon or two of water before it goes in the tank. Pouring it in straight concentrates it in one spot instead of distributing it.

Step 4 — Get it into the system

Gravity fill: pour the diluted solution into the fill port with a funnel.

Water management panel: newer rigs let the onboard pump pull the solution directly into the plumbing. Use the sanitize or winterize setting if the panel has one, and verify valve positions against the manual — this varies a lot between manufacturers.

Then fill the fresh tank all the way with potable water and turn on the 12V pump.

Step 5 — Run it through every fixture

Open fixtures one at a time and run until there's a faint chlorine smell. Run the hot side and the cold side at each one.

• Kitchen sink
• Bathroom sink
• Shower
• Toilet
• Outdoor shower
• Outdoor kitchen
• Any utility faucets or spray ports

The point is getting solution into every line, including the ones nobody thinks about. If there's an ice maker, dishwasher, washing machine, or fridge water dispenser plumbed in, check the appliance manufacturer's guidance separately before running chlorine through it.

Water heater notes

Procedures differ by model, so the manual matters here.

• Leave the water heater off during sanitizing and flushing
• Never run a tank-style heater dry
• Confirm the tank is completely full before restoring electric or propane heat
• If the heater was bypassed during winterization, check whether the bypass should be removed for this process
• Tankless units often have their own procedure

Step 6 — Let it sit

Minimum four hours. Some manufacturers recommend longer, up to overnight. Contact time is what actually does the work — cutting this short is the most common way the process fails.

Step 7 — Drain and flush

Drain the tank fully through the tank drain, low points, and faucets.

Refill with potable water, run every fixture again hot and cold until the chlorine smell fades. Depending on system size, this may take two or three fill-and-drain cycles. Rushing the rinse leaves chlorine taste behind for weeks.

Step 8 — Filters back in

Reinstall what came out, or replace the cartridge if it's near end of life. A new filter on a freshly sanitized system is where the taste improvement actually shows up.

The part that undoes all of it

The system is only as clean as the hose filling it.

Use a hose rated for potable water, store it separate from sewer equipment, cap both ends in storage, keep the ends off the ground, and replace it when it gets worn. A contaminated hose reintroduces the problem within one fill.

Worth doing even if you don't drink from the tank

Plenty of people run bottled water for drinking. The tank still feeds handwashing, showers, dish rinsing, brushing teeth, and the toilet. It's a maintenance item regardless of drinking habits.

Curious how often others are actually doing this — twice a year, or only after storage? And has anyone found the water management panel sanitize setting to work well, or do you still prefer gravity fill?