Clean water in. Clean water out. Every six months, no exceptions. Total time: 5–6 hours (about 1 hour active).
RV fresh water systems are closed, warm, and intermittently used — exactly the conditions that support biofilm growth, bacterial contamination, and off-taste or odor problems. Sanitizing every six months is the baseline. Run the procedure after buying a used trailer, after using a questionable water source, after the trailer sits unused for two months or more, or any time the water tastes or smells off.
The procedure uses diluted household bleach — specifically unscented liquid chlorine bleach, not splash-less formula and not any scented product. The correct concentration is 1/4 cup of bleach per 15 gallons of tank capacity. Stronger is not better; over-concentration damages tank and hose materials and requires extensive flushing. Get the ratio right, fill the tank completely, and run the solution through every outlet in the system before starting the soak.
Run this procedure at least every 6 months. Also run it any time you notice an off smell or taste in your water, after purchasing a used trailer, after using a questionable water source, or after the trailer sits unused for 2+ months.
⏱ Most of the time is the bleach soak (4–8 hours unattended). Start in the morning, soak all day, flush in the evening.
The Formula. ¼ cup of plain bleach per 15 gallons of fresh tank capacity. Pre-dilute in 1 gallon of water before adding to tank. Never pour undiluted bleach directly in. Examples: 30-gal tank = ½ cup bleach · 45-gal = ¾ cup · 60-gal = 1 cup
⏱ Soak: 4–8 Hours Minimum. Leave the bleach in the system for at least 4 hours. Overnight (8–12 hours) is better. Do not use any water during the soak. Set a reminder and walk away.
Clear the Bleach Fully Before Drinking. You may need 2–3 full tank flushes. The water is not ready to drink until it smells and tastes completely neutral.
Eggy or Sulfur Smell — But Only in Hot Water? Your water heater anode rod is the culprit, not the tank. Replace the rod (see Spring Startup Step 4 for full procedure) — the smell typically clears within 1–2 uses.
Use unscented liquid chlorine bleach at 1/4 cup per 15 gallons of tank capacity. Scented or colored bleach leaves residue. Fresh Citrus is not a sanitation agent.
Run the bleach solution through every faucet — hot and cold — and the outdoor shower if you have one. Standing water in low-use lines won't get sanitized by filling the tank alone.
Your nose is the final quality check. If your water smells faintly of chlorine after the final flush, keep flushing. You'll taste it in your coffee and it's not worth rushing.
Add 1/4 cup of unscented liquid chlorine bleach per 15 gallons of tank capacity to your fresh water tank, then fill the tank completely. Turn on the pump and run every faucet — hot and cold — until you smell bleach at each outlet. Close all faucets and let the solution soak for 4–8 hours. Drain completely, then refill and flush with fresh water until no bleach odor remains at any faucet. This typically requires 3–5 complete fill-and-drain cycles.
Sanitize at minimum every 6 months — at spring startup after winterization and again mid-season if you use the trailer heavily. Also sanitize after using any questionable water source, after the trailer sits unused for 2+ months, after purchasing a used trailer, or any time the water has an off taste or smell. Running this procedure regularly prevents biofilm buildup that becomes increasingly difficult to eliminate once established.
Use regular unscented household chlorine bleach (sodium hypochlorite, 5–8% concentration). Do not use splash-less formulations, scented bleach, or color-safe bleach — these contain additives that don't rinse cleanly from water system components. Standard unscented bleach at 1/4 cup per 15 gallons of tank capacity is the correct specification.
Let the bleach solution sit in the system for a minimum of 4 hours — 8 hours is better, especially if the trailer has been unused for a long season or if you're responding to an off taste or smell. After the soak, drain completely and begin the fresh water flush cycle. Do not use the water for drinking, cooking, or brushing teeth until the flush is complete and no chlorine odor remains.
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