Plumbing is probably one of the scariest parts of any build, especially when you have zero construction experience (like me). I’ll take you through my Tiny House plumbing, but keep in mind that there are several ways to do this depending on your preferences.
One thing to note before we get started: my set up is simple. I only have one shower and one sink. I do not have a washing machine, dishwasher or bathroom sink. My toilet is a waterless compost toilet. My system is set up to be on-grid or off-grid and to be water conscious.
To understand this article, you’ll need to learn the following terms: off-grid, on-grid, fresh water, greywater, and black water. Don’t worry, I’ve defined them all below.
What do these terms mean? Off-grid means that you are NOT connected to city water and that your system is self-contained. You might be off-grid when dry camping or parked on a piece of land without city connections. On-grid is when you are connected to city water, such as in an RV park.
I have both off-grid and on-grid options in my tiny house, which I recommend for flexibility in parking. Of course, if you will always have a city water connection, having an off-grid system is not necessary. First, let’s discuss freshwater for both off-grid and on-grid.
First, let’s talk about my off-grid fresh water system. For water storage, I fill a 46-gallon water tank, which is secured under my kitchen counter. I fill this tank by connecting an RV drinking hose (or carrying jugs of water) to my water inlet.
The average American uses between 80 -100 gallons of water a day, so it’s good I am not “average.” I use about 10 gallons of water a day. When I am off-grid, I fill my tank every 4 days.
To heat the water, I have a tankless propane water heater, which is extremely efficient. Read more about it here. For off-grid water pressure, I use a water pump. The water pump runs on 12V and the water heater requires 12V to spark and to protect itself from freezing. My house is wired for 110, so I have a 12V converter to run these appliances. These elements can easily be powered by a gas generator or solar power when off-grid.
When I am “on-grid” (connected to city water) I simply connect my RV drinking hose to the supplied spigot and there’s no need to use my water tank or pump. In the winter, I need to use a heated hose and insulated spigot. More on Tiny House winterization here.
Once the city water pressure was so strong it actually broke my inlet! Since then I’ve replaced my inlet’s plastic fittings with brass ones, and I’ve purchased a pressure regulator.
The plumbing choice for tiny homes is PEX. It’s DIY friendly and lightweight. You will need the PEX piping, crimping tool, brass elbows and fittings to do the jump yourself.
As a note, I also use a low-flow shower head to conserve water. I have not found this to be a problem when washing my hair. I’ll also mention that the water pump I initially bought (pictured below) can be a bit loud. I ended up replacing it with this more expensive and quieter water pump. Both work fine, but if you want the quieter version, go with the one I just mentioned.
Greywater is not necessarily waste. I use biodegradable products for my soaps, shampoo, conditioner, lotions, etc. My greywater consists of these soaps, my body oils, and food products diluted with fresh water. If I had my own land, I would create a drainage system to use my greywater for irrigating my garden, similar to Art’s tiny house system. It’s a great way to recycle!
When I’m off-grid, I use a portable greywater tank. If I’m on-grid, usually at a campground, I connect to the sewer system with an RV sewer hose.
As with fresh water tanks, greywater tanks come in all shapes and sizes. Mine is only 15 gallons, so I have to dump it once a day. I’m actually glad it’s small because I can empty it myself (it weighs almost 100 pounds when full).
Where I dump my greywater really depends on my location. If I’m on at a national park, I dump it at the allocated dump stations. Dump stations are also sometimes available at rest stops. If I’m in a residential neighborhood, I dump my greywater in the nearest sewer drain or I ask my host if I can use it to water their grass. If it’s raining outside, that’s a good time to dump! Any smelly food product is easily washed away by the rain. Consider it this way, most people wash their cars in their driveway. The soaps they are using have chemicals that are substantially more harmful than my greywater.
*As a note, dumping greywater is not legal everywhere. Research your location and use your best judgment.
I did plumb a freshwater line for a possible flush toilet addition in the future (in case I sell my house one day). You can see that above my toilet in the below photo.
This is a very unenjoyable process. You will need to install a black water tank on your tiny house, and then pay to have it pumped out or drive it to a dump station and do it yourself. You can also bypass your black water tank and connect to the sewer via an RV sewer hose.
I’m told that the average full-time RVer has to dump their black water every two weeks. I dump the solids in my composting toilet every 3-4 months. I don’t have much more to say about black water because I don’t have it. My suggestion is to go waterless with a compost toilet.
Here is a diagram of a more complicated Tiny House plumbing system with two sinks and a black water tank.