RV WATER TANK - How to conserve WATER and empty RV HOLDING TANKS.

The RV water tank could be considered the most important item to have aboard your recreational vehicle.

As we all know, water is needed to survive. If you go camping in a campground, you probably will fill up your rv water tank and use their waste disposal service.

We are going here to concentrate more on dry camping, not being hooked up to a campground service and the problematic with water conservation.

When you selected your recreational vehicle, unless it is a smaller unit, it came equipped with a rv water tank (40 to 90 gallons) and two holding tanks as well, grey and black water.

The grey water tank collects the waste from the shower and sinks (bathroom and kitchen) and the black water tank collects the solid and liquid waste from the toilet.

Keep in mind that:

Not only the RV water tank but also holding tanks are a limitation.

Depending on the length of your 'boondocking stay', the rv water tank may or may not have enough capacity.

Somehow, you will have to refill it. Portable 6 gallon water jugs are sometimes used by RVers who do not want to move the RV to the water source.

If you continuously add to your rv water tank, the limitation becomes the holding tanks. This is because the rv water tank is, which makes sense, pretty much twice the size in capacity than the two holding tanks .

If you bring more water all the time, you will surpass their capacity. You will have to empty them and go to a dump station.

There are three elements to manage:

  1. the fresh water usage
  2. its storage and
  3. the waste disposal of both RV holding tanks.

Knowing that the average camper use per day approximately 6 gallons of water, we realize that a 40 gallon fresh water tank will only allow a couple to stay 3 days dry camping.

Without refilling the RV water tank, this becomes a serious limitation.

When refilling, always get your water from an approved water source. Truck stops, gas stations, dump stations are good places. It is a good idea not to use their hose due to possible contamination but have your own.

While boondocking, conservation has to be a way of life.

You do not want to be limited by the size of your RV water tank.


First, the difficulty of refilling depends on how far you are from civilization.

To refill your fresh water tank, you may have to break camp to go to the source of water with the RV or use another vehicle to pick up and carry extra fresh water back to fill up your rv water tank.

In the latter case, RVers either go to the supermarket to get filtered water, use 6 gallon jugs, portable bladder tanks or hard sided polyethylene water tanks installed in the bed of a pickup truck to get water.

In the last case, a small portable DC water pump can be used to transfer the water to the RV water tank. If you get the water directly to your RV from the spigot, always use a flow regulator to control the pressure.

It is a good idea to install a filter on the water line (between the RV and the flow regulator). Keep the filter refrigerated while not in use to eliminate bacteria to build up. The other possibility is to have a filtration system installed on the water line of the kitchen sink.


When its time to empty both tanks, always empty the dirtiest (black water) first.

To properly flush the black water tank, you want to make sure you have enough flow. This is why it is important to wait until your tank is at least two thirds full to help flush all the accumulated tissue and solids.

Always wear rubber gloves. Have your waste hose well connected to the drain.

First open the trap and dump the black water waste. When empty, open the drain of the grey water tank. This way, the soapy water will help wash the waste hose by cleaning all the residues.

Always support your waste hose to help flushing. When both tanks are empty, close the drains and rinse your hose with clean water.

Do not use your fresh water hose for rinsing; have a small garden hose at hand for this purpose in case the dump station does not have one. Store the fresh water hose separately from other hoses and rubber gloves to eliminate any risk of contamination.

Every few dumps, after you are finish emptying the tanks, it may be helpful to pour water softener in both empty holding tanks. This will help to loosen the solid waste from the sides of the tanks. Two cups in one gallon of hot water is sufficient: Calgon powder found at grocery stores.

Only in the black water tank, you can also add a cup of laundry detergent at the same time. The grey water tank already contains soapy water. Occasionally, you can disinfect both tanks by pouring a gallon of liquid bleach in each.

It is also a good idea to use bacterial digestant for the treatment of black water. Have a look at: RV digest it. Find a RV dump station near your location, consulting these sites:

  1. RV dumps Only in U.S.A.
  2. Sanidumps Not limited to U.S.A.

Also, some portable holding tanks exist to carry away the waste to a dumped station without moving the rig. In my opinion, it is a lot of trouble. These tanks are available in sizes of 5 to 32 gallons.

Some RVers use a macerator to grind up the solids of the black water tank in order that it drains into a regular hose to the portable tank.

Provider of portable holding tanks: Barker Manufacturing

DO NOT EMPTY your holding tanks on the ground or in a gopher hole polluting the water bed. It is not different with the grey water tank.



At all time, the quantity of water present in your fresh water tank has to be well monitored. You also have to think of emptying the rv holding tanks on a regular basis.

The general rule is not to use the water stored in your fresh water tank if you do not have to. If you need to, then find different uses for the same water.

Let's look at some examples.

1) When cooking, avoid using a lot of pots and dishes.

Steam or microwave foods if you can. Try to prepare multiple meals at one time.

To clean dishes, either use disposable paper plates that you can burn so no water is used or wipe first the dirty ceramic plates with paper towel to limit the amount of water needed to clean them.

You can lick your plate too if no body is looking !!!

2) Capture the rinsing water from the sinks.

The captured water can be kept in a container beside the toilet to be used as flushing water later. You will then reduce filling up the grey water tank which normally has more use (shower plus sinks) than the black water (toilet).

3) Limit your water use when taking a shower.

Every time you need hot water from the sink or shower, do not waste the first colder water in the drain but collect it (in a pitcher) for other uses (ex: brushing teeth, cooking, coffee etc...)

Have a quick shutoff valve on the shower head. This will cut instantly the flow of water. You can then use the navy shower technique. Get wet, shut off the water, soap yourself, start the running water to rinse.

You can also bring a container (dish basket) with a limited quantity of hot water previously heated on the gas burner, stand in the shower and hand wash yourself. You will be surprised how little water you really need to clean yourself.

You can also take a sponge bath with very little water in using a product called: No-rinse body bath. Another idea is to use baby wipes for a body wipe down. Add about one cup of rubbing alcohol to the package to further moisten them.

4) Limit your water use when washing your hands.

Run a bit of water to wet them, shut off the valve, soap them and rinse. You can use a sanitizing hand product as well. Using 100 % biodegradable soap is a must if you decide to soap in the outdoors.

5) Use an outhouse.

If you are 'boondocking' in a location where there is one, it may be a good idea to use it instead. You can reduce the quantity of black water in your rv holding tank.

6) Wash your clothes in coin machines.

It is unlikely you are going to use a washer (and dryer) inside your rig. The washer would fill the rv holding tank (grey water) very quickly and will have a high demand in energy. The coin machine at the laundry mat is a better alternative.

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