To deodorize grey water, eliminate the root cause: decaying food particles, grease, and soap scum trapped in your holding tank or pipes. You can treat odors using a few simple, highly effective methods.
Grey water odors are usually caused by food particles, soap scum, and body oils breaking down in the holding tank. To control and eliminate these smells, dissolve grease buildup using a specific treatment like Camco TST Grey Water Odor Control or deep clean the tank using dish soap and fresh water.
Baking soda, vinegar and lemon juice are all easy to source, great cleansers and won't harm your plants when diluted and processed through a greywater system. Vinegar contains acetic acid which can destroy the cell lining of bacteria and viruses.
UNTREATED GREYWATER
Yes, you can put Dawn dish soap in your RV black tank, but only in small amounts and specifically for cleaning. It is a popular DIY hack to help clean tank sensors and lubricate dump valves, but it should not be used as a primary waste breakdown treatment.
Your RV smells like sewer when flushing because the toilet is a direct gateway to the black tank. Smells can enter the living space due to a missing water barrier in the bowl, a bad seal, a clogged roof vent, or negative air pressure from running your ceiling exhaust fans.
Grey water systems generally have a lifespan of 10 to 20+ years, largely depending on the complexity of the system and maintenance. Simple laundry-to-landscape systems can last over a decade, while advanced, pumped, and filtered systems often require component replacements (like pumps) within 10–17 years.
If you are driving a certified self-contained vehicle, please dispose of your grey water (sink and shower) and toilet waste in a safe and environmentally sound way at an approved dump station. Campervan companies recommend disposing of your waste every 2-3 days.
Greywater-safe laundry detergents contain zero sodium, boron, or chlorine to protect plants and soil biology. Top biocompatible and greywater-safe brands recommended by experts include Oasis and Biopac. For common store-bought options, ECOS is highly regarded, along with using natural castile soap.
To clean a grey water tank, use a combination of liquid dish soap (like Dawn), water softener (like Calgon), and baking soda. These items break down organic gunk, soap scum, and grease without damaging the tank's sensors or plumbing.
In particular, avoid using vinegar on natural stone surfaces such as marble, granite, and travertine. The acidity can dull these materials over time and may even break down the sealant that protects them from stains.
Liquids soaps are preferred over bar soaps as they have less salts. A pure castile soap, such as Dr. Bronner's, is perfect for greywater as is Oasis dish or all purpose cleaner. For shampoo and conditioner look over the labels to ensure that you are not using a lot of sodium.
To stop your RV holding tank from smelling, use dedicated enzymatic or bacterial treatments (like Camco TST Orange Treatment or Walex Porta-Pak) alongside 2-3 gallons of water after every dump. Alternatively, use a DIY mixture of 111 cup liquid water softener (Calgon) and 111 cup Blue Dawn dish soap.
The characteristic "old age smell" is scientifically known as nonenal (or 2-nonenal). It is a chemical compound produced when the skin's natural oils and fatty acids break down and oxidize as we age.
Using bleach in your RV black tank is generally not recommended. While it temporarily masks odors, concentrated bleach corrodes rubber seals, destroys tank sensors, and kills the beneficial bacteria needed to break down solid waste.
Many Amish households use standard, commercially available detergents like Tide or Gain, as they often shop at the same local supermarkets and bulk stores as non-Amish communities. However, many others prefer to live sustainably and avoid harsh chemicals by using simple, natural, and highly effective DIY detergents.
Unlike other dish detergent brands, Oasis is formulated for greywater and septic systems. Safe for disposal or reuse, you won't release toxins into the environment.
You could also just hook a hose up to it for a gravity flow system. You'd only really be able to water downhill from the tank, though. How far away is the garden where the water is needed? You can extend your hose with a Nylex 34mm x 20m Grey Water Hose if it's not too far.
Food trucks are required to maintain tanks that can store used water. Discharge to an approved restaurant, commissary, or treatment plant that can accept and discharge wastewater to the sanitary sewer.
Empty your grey water tank when it is 23two-thirds𝟐𝟑 to 44four-fourths𝟒𝟒 full or when the shower drain starts to gurgle. Leaving the tank closed until it's full is best practice; a full tank generates the pressure needed to effectively flush solids through your sewer hose when you empty your black tank.
The California Plumbing Code estimates the volume of graywater produced at 25 gallons per day per person for a graywater system collecting the discharge from the showers, bathtubs, and lavatory sinks.
Potential Hazards
All greywater has the potential to harbor dangerous bacteria and viruses. It is never potable. Micro-organisms present in untreated greywater can cause damage to foliage. Untreated greywater should not be used for lawn sprinklers, as this could spread dangerous, airborne bacteria.
Graywater for toilet flushing is more appropriate in commercial or other high-density properties where dedicated staff can maintain it over time. In general, toilet-flushing greywater systems usually require frequent maintenance, manual cleaning of filters, and chemical disinfectant to prevent odors in the bathroom.
Greywater can be safely used for landscape irrigation if it is properly distributed through a drip or subsurface irrigation system. However, it should not be dumped on the ground surface, as it may attract pests, cause pooling, or create unpleasant odors.