RV Water Storage Tanks – What You Need To Know

Last updated on December 29th, 2021 at 12:43 pm. Originally published on April 13th, 2015


When winterizing your RV, you should drain all the water from your holding tanks. Though this can be hard to do, if you don’t manage this feat, some moisture will still be left in the system. This will sit there for the next three or four months. Imagine what can happen with stagnant water in your system during that time. Or better yet, don’t!

Left sealed, the water tanks fill with slime and algae. Bathing or washing your hands in this foul-smelling water is enough to make you never want to go Rv-ing again! This is the same water tank that you will refill with water for doing your dishes, showering and even washing your food with. It’s definitely a bad idea to assume the water in your storage tanks will always remain fresh.

Not only do RV owners have to deal with water systems that have been laying dormant for months, but also different water sources at every stop when they travel. Contaminated water can kill you. Have you ever been told never to drink water in Mexico? Well your RV water storage tanks may be even worse than Mexico’s supply. Also, some refill stops dispense well water, so if you don’t have a filter, you could end up with cloudy water with particles in it. Ensure that you take precautions to get your water as safe to use as possible.

How do you do this?

Firstly, only use white non-toxic hoses to fill your storage tanks. Roll up this hose with the two ends stuck together when not in use. Any other hose may leach chemicals or even make your water smell bad, as is the case with garden hoses.

White water Hose


(Don’t forget to carry a garden hose along to use for flushing your system or washing your RV.)

Secondly, you also need to buy a filtration system if you do not have one. The filter will keep debris from entering your storage tanks and can remove some bacteria and even lead, which is commonly found in drinking water. You can either install an inline filter directly in the kitchen sink you drink from, or simply filter all the water going into your RV. Filter all the water, if possible, otherwise you will be drinking clean water, but showering in filth.

Thirdly, the most important step is to keep your RV water storage tanks clean and sanitized. At the minimum, this should be done once a year when you take your RV out of storage.

To sanitize your tanks:

  1. Drain the water heater first. Release the pressure relief valve first, then open the drain located on the bottom left hand corner.
  2. Locate the low-point water drains and open them so the water can drain completely.
  3. Find the fresh water tank and drain the water in it. Use the water pump to force all the water out. When the water stops coming out of the tanks, turn the pump back off or it may get damaged. Close all the drains when you are done.
  4. What you want to do next is refill the tanks with a mixture of bleach and water. One cup of bleach to 15-gallons of water should be sufficient. Fill your tank, but not completely. If possible, drive around for a bit. Let this water sit in your tank, then open all your faucets and let the water drain out. You should smell bleach in the system. Leave it as it is for another 12 hours at the very minimum.
  5. Drain the tank again as in #3 above.
  6. Refill the tank
  7. Open the faucets and drain it again.

You should refill and drain the tanks until you can no longer smell bleach in the system. It may take a few drains and refills.
Your RV water-holding tanks are now clean and sanitized.

How to install an RV water storage tank

Rv holding tanks
There are three types of RV water-holding tanks: black water tank, gray water tank and the fresh water tank.The grey water tank holds most of the water used in an RV, with the exception being the toilet. The black water tank holds the water used in the toilet. For more information on black tanks, check out this article.

The first step is deciding what type of material your holding tank should be made of. Plastic, polyethylene and ABS are the most commonly used materials.

Next, figure out where the plumbing fixtures are:

  • The black water holding tank should be fitted directly under your toilet.
  • The fresh water holding tanks should be in a central location that will make it easier to hook up to the sink, shower and toilet.
  • The grey water holding tanks should be between the sink and shower.

Use the manufacturer’s instructions to do the installation.
The size of your tank should meet your travel needs and also your measurement allotments and RV Specifications. While planning how to install the tanks, keep in mind the tank specifications themselves. Holding-tank manufacturers can customize the fittings anywhere you specify.
If you are installing larger tanks than were previously there, ensure you have additional support bars.

There are three elements that need to be considered before heading out on any RV trip:

  1. Storage of fresh water
  2. Usage of fresh water
  3. Disposal of waste in the holding tanks

Refilling your water tanks:

Depending on how long you intend to be in the “boondocks,” your RV water storage tanks may not hold your required capacity. You may have to refill your tanks at some point, even if you carry extra fresh water.  (Refilling issues tend to depend on how far out of civilization you go and for how long!) For example, if your fresh water tank can hold 40 gallons of water and you and your travel mate daily use 6-gallons each, you will have only about three days before your tanks will be empty. Portable water tanks are very helpful when you do not want to or cannot drive your RV straight to the water source. (A small portable water pump can transfer water to your tanks.)  Depending on your circumstances, you may need to break camp and drive back to get more fresh water at a gas station or truck stop (but use your own white hose and a filter, due to the possibilities of contamination).

You never know what might be brewing in your water tanks,  and should therefore always take precautionary measures to keep you and your loved ones safe from drinking contaminated water. Ask where the water in your campground comes from and if it comes from a well, ask if it’s tested. Keep your white water hose separate from any other hoses and keep the ends locked together when not in use. If possible, store it in a bag or seal-able plastic. It doesn’t take much to keep your water holding tanks clean and sanitary, but it is a serious matter that needs to be considered.

Limiting water consumption while on the road:

The water levels in your RV should be monitored at all times. The general rule is to not use the water in your RV, unless you have to, and if you have to use it, try to reuse it.

Here are some examples:

  1. Microwave foods to prevent washing dishes. If you cook, cook multiple meals at once, and then store them in your refrigerator.
  2. Use disposable plates that you can simply throw away. If you do use regular plates, lick them clean or use a wet wipe to get most of the food off first, then rinse.
  3. Use a bucket to capture the rinse water, which can then be used to flush the toilet.
  4. Don’t take a shower in your RV unless you have to. If you do, the first water that will come out of your tanks will definitely be cold. Do not waste this by letting the water run until it gets warm. Capture it in a container and use it to make coffee, brush your teeth or even to wash fruits and vegetables with.
  5. Get wet quickly then turn the faucet off. You can now scrub yourself clean with soap. When you are ready to rinse, turn the water back on and do it quickly. You can also take a sponge bath.
  6. Use hand sanitizer that does not require water, or wash your hands like you shower: wet, the turn the tap off, soap up and then rinse.
  7. Use an outhouse if there is one.

We tend to take clean, flowing water for granted, but you will quickly realize how valuable a commodity it truly is, when its supply is severely limited.

Dumping and flushing your holding tanks:

Whatever the case of your fresh water usage and storage needs, you will eventually exceed your holding tank capacity and have to go to a dump station.

There are several steps to this process:

1. Always empty the black water first. You need to have enough flow to empty your black water tank properly. This is why you should wait until it is almost full so the solids don’t get stuck in there. (Wear gloves and ensure your hose is properly fitted to the drain to avoid getting messy.)

2. Open the valve and dump the waste.

3. Drain the grey water next. If you only have one hose, doing this will “clean” out the muck left in the hose by the black water. After you are finished draining the grey water, rinse the hose with clean water. (Do not use your clean water hose to do this… keep it entirely separate from this job to prevent contamination.)

4. To keep solids and other residue from sticking to the sides of your black water tank, pour some softener in the empty tank. Two cups of softener mixed with 1-gallon of water should do the trick.

5. Use bacterial digestant also to treat your black water.

There are portable holding tanks available for this job, as well. but this can get messy, so it’s much easier and cleaner to simply drive to the dump station.

RV Dump Station

NOTE: Do not dump your black or grey water anywhere other than at a dumping station!

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