RV Water Tanks

Electric and sewer.

Sewer hose stretched out to a rear dump, with the electric going across it. I will not cross water with sewer. The sewer hose is likely to have more germs than I want on my water hose.

The weirdest things about recreational vehicles of most sorts are the water systems.  This is mostly because it requires management at a minor or major level almost no matter how one uses their RV.  Waste water is ‘one of those things‘ in an RV’ers life. It is the kind of thing that would keep some people out of the RV world completely. For almost all of the rest of us ‘RV People’, it is a necessary evil.  For me, it is a source of pride that I have ‘scientifically’ developed a systemic solution set for my RV’s water and holding system.  Over the years, I have developed many hypotheses and tested the hypothesis promoting to an operating theory or rejecting as shown by the evidence.  I have reviewed other folk’s hypothesis, often testing them in the field collecting anecdotal information from stories both directly and indirectly through other information sources such as YouTube, blogs and even old-fashioned magazines.

Generically, RV’s have three basic water systems that are interconnected by faucets, sinks and drains.  Water enters the system from one or two locations and exits the system from one or two other locations.  Fresh water can be stored in a tank for later use and taken directly from the spigot.  Used water from the sinks, usually kitchen and bathroom, flows into the grey water system which generally includes at least one tank called the grey water tank or just ‘grey’ tank.  Toilet water flows to at least one black tank.  The grey and black tanks drain through pipes to one or more fittings under the trailer.  There are several kinds of either built in, added in or portable methods to rinse out the black tank which is important for long term care of the system.

Having the soul of an engineer, I have fully planned methods of dealing with my four tanks (Yes, three systems, but four tanks.  I didn’t design it, I just bought it COTS (Commercial Off The Shelf), so to speak).  My four tanks are Black, Grey 1 (shower), Grey 2 (kitchen) and Fresh Water.

The black tank is for most folks the one they will have issues.  There are a number of methods discussed in the literature/YouTube to prevent problems or handle them once they occur.  My black tank is large enough for two people to use it regularly for 7-10 days without filling it to ‘full’.  My bride and I have gone to 10 days once or twice, but once at 8 days it was FULL.  We don’t restrict flush water use, but I use any off-board option when it is convenient.  For me convenient means that if I am in the trailer, I don’t put on my shoes, run down the stairs and across the campground, on the other hand, if I am outside I will walk to the nearest toilet rather than climb back into the trailer and I am perfectly capable of peeing in the woods, while my bride does not use either of those methods.

After a lot of reading, years of my own experience and plenty of less than pleasant outcomes, I have developed a routine, with variations, to handle waste. This is the point where I am going to discuss in great and glorious detail the systemic handling of waste and water in an RV.  If you don’t need it now, but think you will later, bookmark it and go on about your business, although it is absolutely fascinating, if for no other reason than I have written pages and pages about shit and management of said shit.  Also, this is specific to my rig, your rig will be different, but generally speaking, it wouldn’t take much to modify this to your specific system.

If you don’t own or plan to own a Recreational Vehicle of some sort some day, there is probably not much left in this article for you… ;-), but on the other hand, it is a short read and you’ll know something your friends only dream about.

Moving Day

I am one of those guys that takes forever at the dump station.  I do try to hurry it up if there is a real line and I try to time my exit away from the rush if I need a clean empty tank, which is usually.  Not to overstate the obvious, but it is much easier the last day in a full hook-up site.  This general routine when packing up to move:

My black tank rinse hook up is easily accessible. Notice the hand cleaner and sanitizer. I rarely wear cloves because they end up being more of a pain than just washing five or six times while I work. I keep sewer gloves around just in case something bad happens, but otherwise I sanitize, sanitize and scrub.

  1. Attach the wast drain hose and open the black tank valve.
  2.  While the initial empty is happening, I hook up my wash hose to the tank rinse fitting.  This is a regular garden hose that I use for this and washing the rig or furniture and the like.
  3. Run the rinse for a few minutes with the tank valve open.
  4. Close the black tank valve allowing at least 10 gallons (~25%) to gather in the tank. I set my watch timer, because the consequences failing to turn it off are monumentally bad.  10 minutes will usually be enough, but a few minutes more if the pressure is low and if by some strange occurrence that I have never experienced a little less if the pressure was unbelievably high.
  5. Dump again. From watching the flow at my clear elbow going into the drain, if I see additional material coming out I may do the partial fill and rinse again.
  6. Generally, I leave a couple gallons or so of water and a couple oz. of TST (Obviously, the black tank can get stinky. To keep the tank clean and ‘fresh’, I use the product called TST which is available at most RV places, Walmart and probably Amazon, there are many other products, but I like TST and it works effectively.)

–I figure that will give the leftover sediment time and motion on the road to breakdown.

–Alt 5.  If we are heading to a long dry camp I don’t leave any water in the tank, BUT I put 4 ounces of TST into the tank.

–Second Alt 5.  If I am going to storage and I know I will be doing only weekend camping next trip, I tend to put more water into the tank because more always is better in my universe.

  1. Close the valve on the black tank. Open Grey 2 (kitchen).  Kitchen water is stinky and often has particles in it, so it is always second (after black and before Grey 1 (shower)) on my rig.
  2. Close Grey 2, open Grey 1 (shower). I may drain the grey tanks other times, but I try to have a large amount of Grey 2 on ‘Move Day’ as that rinses the sewer hose better than anything else.  Also, it is a good excuse for an extra-long hot shower the day before pack up.
  3. Close Grey 1, disconnect and rinse the sewer hose.  Don’t forget the elbow fittings.

–Side note: For long periods at a Full Hook Up site, leave the grey tanks open, but CLOSE the black. If one leaves the black open the water and liquid waste will run off leaving the solid waste to pile up.  Use these times to get a feel for how long you can go before emptying your black tank.  A couple of days before emptying the black tank, close the grey valves to build up hose rinse water and clear out any grey tank residues.

One of the interesting (it the sense of quirky) things is that many of these tanks have sensors to show the content level of the tank.  I envy the folks whose sensors work and many do, but it seems that most do not work effectively, i.e. they are rarely correct.  I don’t know what the difference is: type, brand, placement, but in three of my trailers that had water and sanitation tanks, the tank sensors never worked well enough to be of any real use.  Figuring out how long tanks last in different situations is the only answer for me.

Dry Camp

At dry camps, waste water is a different problem altogether.  Like I said, I have 7-10 days capacity on the black tank and generally similar with Grey 2 the kitchen tank.  But Grey 1, the shower, and the Fresh Water are another story.

My wife and I shower in the trailer.  Although we are very conservative in our water use while showering at dry camps in that we take Navy showers (water on long enough to get wet, water off, soap up, water on long enough to rinse, water off), it still translates to filling Grey 1 (shower) waste tank and emptying the fresh water way too often.  Since we are generally not going to change that behavior, I have developed ‘methods’ and if those methods are unavailable, campground showers and sponge bathes are the order of the day, but in my experience that has rarely been required.

Dealing with said shower grey water is dicey at best. I only use my ‘methods’ if I am in a place that it is ok.  Ok in the sense of ‘First, do no harm’.  The best situation is when there is foliage that would benefit from a bit of extra water and no one who would be affected near me.  Generally speaking this can only be used in primitive campgrounds with widely spaced sites and dispersed camping.

Channel locks that just stay here and the sewer cap with a garden hose bib.

Using a sewer cap with a garden hose fitting and draining shower water through the same hose I use for washing out my tanks.  I put the output end into the bushes and preferably down hill.  At my father-in-law’s, while I was driveway camping, I drained the grey onto the leach field for his septic system.

Again, this is often frowned upon (sometimes forbidden) and obviously shouldn’t be used in busy or crowded places (also not usually required in those places).  A hundred or more feet of drain hose gives me the flexibility to pick a reasonable spot down hill and away from me or others to let the ‘grey-water fairies’ do their business.

Kitchen doesn’t get full as often and that water stinks, so I generally don’t drain it off in the bushes.  We do use regular dishes for dinner and wash them, but reasonable conservation is pretty effective in not filling Grey 2.

Keeping the Fresh Water Tanks Full

I have two methods for filling the fresh water tank at dry camps, The Hose Method and The Pump Method.  These are my tools and the methods have a high degree of variability based on the campground layout.

If I can, I use hoses, but it is worth it to me to haul water 15 gallons at a time to have a shower in my own shower (even a short Navy shower) and running water for all the other things in life.  So here are the two lists of equipment that I currently have the methods are direct functions of the equipment and I think they self-explain, if not ask the questions/point out the omission in comments and I’ll get back to you.

1. The Hose Method Equipment

Hose box with several water hoses.

Hose box. Any given time there are three to five hoses in there. Mostly just a pack-rat thing

  • 20’ or 30’ drinking water hoses.
  • I ended up with 100’ drinking water black cloth covered hose from Lowes that specifically stated that it was good for drinking water, it compresses well and is tough enough for cars to drive over it.
  • ‘Water Bandit’ to attach to spigots without threads.  Once you see it, it self explains.  Sort of works, sometimes, but not always, hence the pump.



Water Bandit

Water bandit. Works so-so, but better than nothing.

2.  The Pump Method Equipment

The electric pump system

The electric pump system. All fits in the bucket. The cord is a worn out extension cord repurposed with some clamps also repurposed.

  • 12-volt water pump (bought on Amazon and specifically is ok if it runs dry).
  • Clear hose cut in two to the best lengths for your system to get the water from the jugs to the tank

-One end of each clamped to the pump.

-Upstream hose has nothing on the end

-Downstream (into the trailer system) has a threaded fitting because my fill is designed to screw in a water hose (many just have a hole, sometimes the same opening acts as overflow in which case just the hose end will likely work)

-Short piece of PVC that the hose fits through to keep it on the bottom of the jugs while pumping, and threaded fitting to attach to the trailer’s fill fitting at a local hardware store.

12 Volt electric water pump with clear hose and fittings.

12 Volt electric water pump

  • Two 5-gallon collapsible jugs and a bucket that does double duty as one water carrier and it holds the whole kit for storage.
  • Folding cart (bought at Costco and used for laundry, groceries and grand-children)

Fresh water at full hook up sites

Just a couple of notes about hooking up for fresh water.

  1. Always use a pressure regulator prior on the freshwater hose before water enters the trailer.
  2. I installed and change out every six months a ‘whole house’ water filter before water even enters the trailer.  Not all campground water systems are stellar.
  3. I don’t always like the water flavor at campgrounds.  I installed a two stage water filter with a separate spigot from a chain hardware store.  It was a pain to install because house water is piped and RV water uses hoses though out the rig to get water to the faucets.  I suspect there is a better solution available at an RV shop, I just didn’t have one available at the time.  I like the two stage set up and the carbon really cleans up the taste.
  4. Yes, that would be two different filter systems both of which have a date marked with a permanent ink marker on the side.

The Hundred Foot Box

One of the things I have recently ended up with is a ‘hundred-foot box’ which has a hundred foot each of fresh water hose, grey drain hose and electric cord.  The 100′ 30 amp rated cord was for driveway camping at my father-in-laws. I’ve had the grey hose and previously it was a ‘suspect’ water hose (I suspected it might not be ‘certified’ drinking water safe, but figured for short term use, like filling the Fresh Water tank, it was probably ok).  I found a drinking water safe, 100′ hose that stores relatively compactly at Lowes (on sale too).  I had an unused storage box in my basement (when I leave for a long trip I like to have a couple of empty plastic boxes for the whatevers we find) which nicely holds all three.  Each has been in use and was added for a specific purpose

Other Ideas and Thoughts

That covers the basics of my system, but while writing I have been thinking about other things I have heard and read about.  One is the ‘ice cube thing‘ for the black tank which consists of putting a bag of ice in the nearly empty black tank just before heading down the road. I saw a YouTube demonstration that ‘proved’ it doesn’t work, but lots of folks use it and swear by the method.  I think it might work in a completely empty tank to break up some of the sediment dregs on the bottom of the tank, but thorough and regular rinsing and chemical treatment probably work better.  Besides my bride uses up all of the ice we bring with us anyway.

Another methodology is trying to go longer between dump station visits by limiting liquid in the tank (urine or water).  As if the subject isn’t gross enough, this method can get as extreme as in putting used toilet paper in a trash can instead of the toilet.  I met someone who used this extreme method.   They were having a lot of problems with their black tank, if I understood her correctly, the tank was clogged up and wouldn’t drain.  I am of a mind that this method is asking for trouble with a system that is a serious pain if it needs work.

This last issue is similar.  I hear folks not using chemicals at all or ‘cheaping out‘ by not using very much of whatever chemical.  TST and the other brands are relatively inexpensive.  I don’t stint on it.  I use 2-4 ounces after every dump station visit and I will add a couple of ounces more every three or four days on a long stay.  My reasoning is the same as before, a broken blank tank system is expensive, smelly and/or just a serious pain to fix and even a stuck valve is a hard to accomplish repair job.

Also, for those of you that have been doing this for a while, you may notice that I don’t address the portable tanks used to haul waste to nearby dump station. I don’t use one because the portable tank takes up too much storage space while traveling.  I either stay someplace with full hookups or keep moving from place to place so dumping is just part of the move process.  As I said, a week is easy and usually enough for me to see what I came to see–time to move… We’ll see what the future holds, I can see the value just haven’t had the need.

In Closing

As someone else pointed out, this is a subject with a lot of answers, but this is mine and it has grown up around my experience with three trailers.

When I was a Boy Scout leader one of our health worries with the boys while backpacking was constipation.  This was a problem with multiple causes, but primarily because trail food is different from home food and one is often pooping in the woods which for some brings up shy bowel problems.  KYBO became the word of the day and the name for outhouses.  The most important thing about the care and maintenance of an RV tank system is that if the system works you are much more likely to Keep Your Bowels Open by using it as needed for your health and safety.

I would be glad to answer questions in the comments.

Good luck and KYBO

  5 comments for “RV Water Tanks

  1. Dennon Mills
    December 2, 2018 at 23:47

    Great article for a rookie like me. Please comment on the instructions I received from a Lazy Days RV professor. He said: never empty black tank until it is at least 3/4 full. Immediately refill with to at least 1/4 and add capful of TECHrx . NEVER put ANY other product in the black tank.

    • rayrogers10
      August 27, 2019 at 03:08

      Hey, just figured out where the comment approval screen is on WordPress, always something new to learn. As far as your professor, it just sounds impractical. Sometimes I push my tank to too full and other times I empty after a two day weekend trip. I like putting a lot of water in the tank when I am heading to storage and occasionally when I have stressed the system with long periods of partially filled sitting around because I got lazy or busy. On the other hand, if I am heading out to dry camp for a week or so filling to 25% of my capacity would be counter productive. As far as his suggestion on the magic chemicals, I’ve never seen it or heard of it which leads me to a two fold conclusion not easily available and probably not actually needed. Chemicals for holding tanks are old technology so there are lots of perfectly fine options. Good luck.

  2. rayrogers10
    October 25, 2018 at 17:49

    From my friend Greg: What are your thoughts on sanitizing the fresh water tank occasionally? Also, I think the ice method could work but would require chunks larger than ice cubes. Small cubes wouldn’t have the mass to break stuff up.

    • rayrogers10
      October 25, 2018 at 17:50

      I shock the tank once or twice a year. Bleach mix, 1/4 cup for every 15 gallons mixed into a gallon or two of water. Put the bleach solution in the tank, fill the tank full and run it through all the faucets even the toilet with the water pump. One advisor suggested a long drive on a curvy road to be sure all the tank inner surfaces get touched. Half hour is a quarter past done. I also drain my tank regularly to keep the water 🚿 fresh and wholesome.

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