RV Holding Tanks – Fresh, Gray And Black

Something that often isn’t thought about when people dream of living in an RV is how to handle the fluids we use – and wastes we produce – in daily living.  While not pleasant to think about, they are a fact of live and you need to consider them!

If you are used to living in a stick house they you are accustomed to rarely having to worry about your water.  You turn on the tap – water comes out, you pull the plug on the sink or flush the toilet, and water and waste is whisked away.  Your chief chore is to pay the water bill once a month.

Unfortunately, RVs require a little more thought about such things.  Don’t worry however; while it may not be pleasant to deal with wastes in a recreational vehicle, it really isn’t that difficult. First, some background.  Most RV’s have three different tanks for water.  These are the fresh water tank, the gray water tank, and the black water tank.  So, what does each of those do?

Fresh Water Tanks for RVs

The fresh water tank is pretty straight forward – it is like a big water bottle for your RV that supplies water when you are not connected to a permanent source.  Whenever you need water for activities such as showering, washing dishes, cooking, or flushing the toilet; it is drawn from your fresh water tank.

The size of this tank will depend on your vehicle; on a small trailer like a Casita it may be at little as 12 gallons, while if you own a large Class A Diesel it may be 40 gallons or more.  Your RVs fresh water capacity can be a limiting factor in the time you can spend on activities like boondocking, but carrying extra potable water in your tow vehicle can stretch your supplies.

RV Gray Water Tanks

Gray water is non-sewer water that you have used in your RV.  Water that has gone down the drain in the shower, or in sinks in the bathroom and kitchen goes to the gray water holding tank. If you take long showers in your RV, you may find yourself filling this tank quite regularly.

Owners of RVs with small gray tanks often purchase an additional tank to provide extra storage, which is connected to the grey water drain by a short hose.  These ‘blue boy’ portable tanks can get very heavy however, and even those with built-in wheels you may find are not particularly portable.

Black Water Tanks

Black water is the sewerage of the RV world.  When you flush your toilet the waste goes to the black water tank.  As you can imagine, problems with this tank can result in a big stinking mess; thus proper operational procedures are a must!

Be sure to use appropriate chemicals in a black tank.  There are various enzyme based chemicals available on the market designed to break down your waste, and also remove smells.  A wise RV’er makes use of these chemicals every time they dump their tank.

Don’t flush just anything down your toilet, the only thing that should go down there apart from your organic wastes should be toilet paper designed for RV use.  Regular toilet paper can cause clogging. No paper, napkins, tissues, etc… should be flushed down the toilet – including feminine hygiene products.  Dispose of items like this in your trash, not in your toilet.

Managing your Waste Water Tanks

There are two basic options for your black and gray water tanks at any particular campsite.  You can operate self-sufficiently, i.e. without sewer hookups, or else connect to a campground sewer system.  Either way you need to possess sewer hose(s) to drain your tanks.

Rule number one – never use a gray or black water sewer hose for moving around fresh water, and likewise never use a fresh water hose for your waste water.  I think the reasons for this are obvious!

Try to keep your black water tank in a state so that there is always fair amount of liquid in it.  If you have a lot of solid waste without much water to dilute it, you are likely to get smells – or even clogs.  After draining your black water tank place a little clean water in the bottom with some fresh tank chemicals, this will help keep odors down.

If you do choose to hookup to a sewer system, it is advisable not to just drain directly into it.  Instead keep the valves closed until you ready to drain.  This means the chemicals you add to your tanks don’t drain straight to the sewer – giving them a chance to work their anti-odor decomposing magic.  It will also prevent any stench in your campgrounds sewer system from finding its way into your home.

Dumping Your Tanks

No matter how you travel with an RV, at some point you are going to have to dump your waste tanks.  Remember this – never dump your black water tank except at an approved dump station!  There are certain circumstances where it is ok to dump you gray water – perhaps via an adaptor to a garden hose to water a garden – but I advise that in general you should aim to do this at a dump station also.

You should have a couple of heavy duty sewer hoses like the Rhinoflex pictured (it is always good to have a spare).  Don’t go cheap on these items, saving a few dollars on a cheaper model is not worth the increased risk of tears or leaks when you are dealing with raw sewerage!

Always dump your black water first – preferably not until it has a substantial amount of fluid in it, to ensure the best possible flush.  Dump the grey water tank second, as the cleaner water in this tank will help clean the sewerage from your sewer hose.

If you are ready to dump your tanks but there is not much in them – say for example you are taking a long trip, or putting your RV up for a while – then go ahead and add some additional water until both black and gray tanks are two thirds full first.  This additional volume will ensure more of the undesirable contents flush out.

After dumping, thoroughly flush both tanks.  This may take a bit of water, but it is well worth doing to ensure you remove as much odor causing material as possible.  Finally, be sure to add a little fresh water to the bottom of each tank, along with your normal holding tank chemicals.  At all costs you should avoid holding tank sludge buildup.

While nothing can quite prepare you for the experience of dumping your tanks for the first time, thinking the process through carefully ahead of time and not taking shortcuts will maximize the chance of avoiding issues. If you want to see what dumping the tanks looks like, check out this video (courtesy of RV geeks).

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