Tiny house plumbing can range from simple to (very) complicated.
A tiny home built on a foundation will have plumbing that is similar to a standard home’s plumbing while a tiny home on wheels will have plumbing that is more akin to an RV’s plumbing system.
In this post, we’ll cover everything about plumbing systems for tiny homes on wheels.
A tiny home no wheels will need to have water tanks. These water tanks make it easy for tiny homes to use their plumbing systems while in transit.
Freshwater tanks, black water tanks, and gray water tanks are the three tanks you’ll generally see in a tiny home. However, some tiny homes will only have fresh water and gray water tanks.
Here’s your basic info about these water tanks.
Fresh Water Tanks
Freshwater tanks are used to store clean water. These tanks can be filled up with a hose and are usually plumbed into the kitchen and bathroom.
The freshwater tank is usually the largest of the three tanks as it will end up emptying out into both the gray water and black water tanks.
These tanks can hold a lot of water so some people will empty them before traveling long distances to cut down on weight.
Using the Water
Using water from a freshwater tank isn’t as simple as using a faucet inside of a home connected to city water. This is because there isn’t any pressure to drive the water from the fresh water tank and up to the faucet.
Because of this, you may have to install a water pump to pump water from the fresh water tank up to your sinks, toilets, and shower heads.
These water pumps will need to be able to sense when they are needed and when they are not so that they do not pump water up to the faucets at all times.
In order to run these pumps, you’ll need electricity. This means that if you decide to put plumbing into your tiny home, you’ll also need to put electricity into your tiny home.
An off-the-grid plumbing system will also need an off-the-grid power system. As a result, you’ll need to make sure you have batteries in your tiny home as well as a water pump that runs off DC power. If you want to run an AC water pump, you’ll also need a power inverter.
When you’re connected to a water source, you may not have to worry about having a water pump to pump water up to your faucets.
This is because the water from the water outlet will be pressurized and it will run out automatically as you open up your faucets. However, you won’t have to worry too much about this since campsites with water hookups usually have electrical hookups there as well.
Black Water Tanks
A black water tank stores the wastewater that comes from the toilet. The water stored in this tank is toxic and should only ever be emptied out into a dump station.
This tank is usually the smallest of the three tanks. Sometimes tiny houses only have one wastewater tank that holds both black water and gray water.
For more information on this type of water tank, see our post titled, “How Does an RV Black Water Tank Work“. This post was written about RVs but it applies to tiny homes with black water tanks as well.
Gray Water Tanks
Gray water tanks hold water that has come from the shower and the sinks. This water does not hold any human waste but it may have kitchen scraps and soapy water from the shower. You should never empty this water out onto the street as it will enter storm drains and pollute local water sources.
In some areas, you can empty this water out onto the grass or dirt. For example, some homeowners might empty their gray water tank out onto their yard.
This is generally considered safe for the environment since the water will have a chance to be filtered by the lawn before it has a chance to enter into local bodies of water.
The fresh water tank can be filled with a hose or at a water outlet at a campground.
Water pressure can be strong at these campgrounds however, so it is important that you bring a water pressure regulator to help manage the speed of this water entering your plumbing system. Fill a tiny homes water tank with highly pressurized water and you may end up developing leaks in your pipes.
If you find yourself in an area without a hose, you can always fill the tank using large water jugs and a funnel. This being said, some tiny homes have 100-gallon tanks so it usually isn’t very efficient to fill it up this way.
Freshwater tanks will always be emptied out into the gray water and black water tanks. Gray water tanks can be dumped at dump stations or sometimes onto the ground. Blackwater tanks must always be dumped at dump stations.
All tanks should have meters installed in them that let you know if the tank is full.
This will help you manage the tank and will ensure that your pipes do not end up backing up on you.
To dump a tank, you’ll need a sewer hose. The sewer hose is connected to a pipe in the ground that goes into a holding area. Always hook up the sewer hose before opening up the tanks and always do one tank at a time. It is best to empty the black water tank first so that the water from the gray water tank can help to clean the sewer pipe.
Hot Water Options
Hot water is created in a tiny home the same way it is created in a standard home. A hot water heater is built into the tiny home and this water is plumbed to the shower and to the sinks. If the tiny home has laundry appliances, the hot water may be plumbed to them as well.
Tiny home hot water heaters are usually either gas or electric, with gas being more common. Gas hot water heaters are nice for off-grid situations but electric hot water heaters are better for campgrounds. This is because short-term stays at campgrounds usually include electricity so you end up getting free hot water while camping.
A hot water heater in a tiny home will be small so you’ll have to manage how much hot water you use at once. Most tiny home hot water heaters are between 2.5 gallons and 10 gallons. This is much smaller than the typical 40-gallon hot water heater you usually find in a house or an apartment.
If not having a lot of hot water to use is a problem for you, you may want to go with a tankless hot water heater. These hot water heaters provide instant hot water but they are more difficult to install. Also, these hot water heaters are power hungry so you’ll need to have a good source of power to run them.
This being said, an instant hot water heater does not need to be turned on all of the time so you will save some energy there. Just be sure to remember to turn it on a few minutes before you need it so that it has some time to heat up.
Connecting to Hookups
When staying at a site with full hookups, you’ll need a sewer hose and a freshwater hose as well as a water pressure regulator. Usually, you’ll hook up to the sewer first and then hook up your freshwater source.
Staying at a campsite with full hookups is nice because you won’t have to break camp to empty out your tanks. If you happen to find a site with freshwater only and you don’t want to have to break camp to empty your tanks, you’ll need to get portable tanks to empty your waste into.
Every tiny home is different and some people have found creative ways to obtain water or to get around using water in their tiny home at all. Wastewater tanks can be avoided through the use of specialized toilets and freshwater tanks can be filled up with rainwater instead of from a tap.
These types of alternative solutions can often be more complicated but they do make going off the grid a bit easier. Also, in some cases, an alternative solution may end up being less expensive to own and to operate.
Composting toilets come in many different forms but they all have one thing in common.
These toilets do not use water and therefore do not require the use of a black water tank.
A composting toilet will store waste inside of it until the owner of the tiny home finds a place to dump it. These toilets can fill up quickly and dumping them can be challenging for people without outhouses that they can access.
This being said, properly used composting toilets can be great for the environment as they recycle the waste and do not use an unnecessary amount of water. They can also be great for people who do not have access to dump stations.
An incinerating toilet works by burning a toilet’s waste. Usually, these run on propane gas but they can run on natural gas and even electric. These toilets burn the waste until nothing remains but a small amount of dust.
Over time, waste that cannot be fully incinerated will need to be removed and discarded but this process is much easier and simpler than getting rid of waste from a composting toilet. In most cases, people will just pull it out and throw it into the trash can or bury it in the ground.
A cassette toilet has its own black tank built into it. These tanks hold anywhere from 3 to 7 gallons so they need to be emptied frequently. The nice thing about these toilets is that you can dump them in any standard toilet.
This means that instead of going to a dump station, the tiny homeowner just needs to visit a rest stop to empty out their cassette toilet. A cassette toilet usually doesn’t cost much to buy and because plumbing and a black water tank are no longer needed, much of the complexity of the plumbing system is done away with.
Rainwater Catchment Systems
Some tiny homes use their roofs to help them gather rainwater from drinking. These systems require a pitched roof, a gutter, a tank, and a filtering system.
Rainwater catchment systems are great for areas with lots of rain but they can be frustrating in many parts of the country. On the positive side, they generate free water that can easily be accessed while off the grid.
Also, areas with a lot of rain will call for smaller freshwater holding tanks which are less expensive and less heavy.
Plumbing Maintenance You Should Know About
The plumbing systems in a tiny home require more maintenance than the plumbing systems in a standard home.
This is because a tiny home on wheels has extra challenges that need to be accounted for.
With a tiny home, you have to worry about all the usual issues like leaking pipes and broken faucets, toilets, and shower heads as well as dirty tanks and frozen pipes. Sure, pipes can freeze in standard homes, but they’re more likely to freeze in a tiny home.
Tanks need to be cleaned regularly. In fact, many experts recommend that the black and gray water tanks be cleaned each and every time they are dumped. This helps remove debris from the tank sensors and helps to ensure that waste does not get stuck in the tanks or within the pipes themselves.
To clean a tank, a special hose is required. Alternatively, a toilet wand can be purchased to clean out the black water tanks. This wand basically gets pushed down into the toilet and water is sent through it to clean out the tank.
Protecting Pipes from Freezing
A tiny home on wheels is much more vulnerable to the weather than a standard home. This is because, with a standard home, you can bury the pipes. With a tiny home, the pipes and the tanks are all sitting at least a foot above the ground and cold wind can easily blow through them.
To prevent these pipes from freezing, tiny homeowners in cold climates need to take a few steps. The first step is to wrap the pipes so they aren’t as exposed. Next, wrap skirting around parked tiny homes so that the wind can’t just blow right through them.
Additionally, heat needs to be sent into the areas surrounding the pipes to help keep them above freezing. This is known as heating the basement of the tiny home. Gas furnaces with heat ducts are great for heating these areas as they work fast and are efficient at sending heat through.
The drawback to this is that these heaters can become costly in cold areas as propane can be used very quickly.
Alternatively, electric heating systems can be built into the floor of a tiny home. These heating systems are usually radiant heaters that also help to provide a never-ending supply of hot water. This is nice for tiny homeowners with luxurious bathrooms and kitchens as they won’t have to limit themselves when running the hot water.
Driving a Tiny Home with Water Tanks
Driving with full water tanks isn’t good for the tanks as it puts a lot of pressure on them. It also isn’t good for your trailer or your vehicle as it adds an unnecessary amount of weight to the trailer.
This reduces gas mileage and limits the amount of other gear you can take with you before going over your weight limits.
On the other hand, it isn’t a good idea to travel without any water in your tanks either. I’d advise that you put some clean water down into your black water and gray water tanks with some tank cleaner added to it. The movement of the water through the tank combined with the cleaner will help to clean your tanks while you drive.
Also, leave at least a few gallons of water in your freshwater tank as well. This will give you some water to use while traveling and will ensure that you’ll have some in case you run into an emergency.
Tiny home plumbing should be well thought out in advance so that you can get the most out of your tiny home.
You can choose between grid-connected plumbing solutions, solutions that work off-the-grid, and solutions that work in both situations.
The last option will give you the most versatility but it will require the most work.
Off-the-grid solutions can become complicated but they can also be more simple than a grid-connected one as they usually require less equipment and less plumbing in general. Think about how you’ll be using your tiny home and choose the plumbing system that best meets your needs.
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Maria is the founder of GoDownsize. While studying architecture in Denmark she became fascinated with designing living spaces for boats, tiny houses, RVs, and other small spaces.
She mainly writes about space optimization, interior design, and downsizing. She’s also in charge of our YouTube channel. Read more about Maria here.