Tiny house plumbing isn’t as complicated as most people think. For the most part, the components are pretty similar to what you would find in the RV industry and traditional housing. How those components line up depends entirely on how you live.

So, how does plumbing work in a tiny house? If you live on-grid, you will be connected to city water and other utilities, including the sewage system. If you live off-grid, you will have your own water tanks and you’ll be responsible for emptying out its contents. 

Plumbing in a tiny home is straightforward once you figure out your needs. Read on to learn the basics of tiny house plumbing, and how to build one for your very own home.

Is Your Tiny Home On-Grid Or Off-Grid?

Your tiny house’s plumbing system will depend on your lifestyle. If you’re living on-grid (meaning you are connected to a supply line either from the city or an RV park), your plumbing would look similar to the set-up you see in traditional homes. Your home is supplied by the city line and your septic system is automatically filtered through your location’s sewage system.

Plumbing for a tiny house on wheels is a little bit different. Most off-grid homes (meaning you are not connected to any supply lines) depend on portable tanks for water and waste storage, but we also recommend getting utility hook-ups. A hybrid system is better than an exclusively off-grid one because it allows you to take advantage of the plumbing utilities when you’re at an RV park or campground. 

Tiny House Plumbing Basics: The Parts and Pieces 

Water Tanks 

A tiny house uses three kinds of water tanks: a freshwater, a greywater, and a blackwater tank. If you choose an incinerating or composting toilet, you wouldn’t have to worry about having blackwater. For some people, this is a much easier option since they don’t have to think about blackwater disposal, which can get pretty tricky. 

People with tiny homes have more flexibility than RV owners. When purchasing an RV, the unit is typically already fitted with its own tanks with predetermined capacities. On average, mid-range RVs could have 65 gals on freshwater, 25 for greywater, and 30 for blackwater. But for tiny homes, the ratio can be adjusted depending on your usage. 

Freshwater 

The freshwater tank stores the clean water you will be using in your tiny house. This is generally the largest tank in your tiny home and is designed to provide enough fresh water for at least a week of use. 

Freshwater tanks can have different sizes and shapes, but it’s generally designed to hold more than grey or black water tanks. A freshwater tank typically holds 20 to 100 gallons of freshwater. Unlike RVs, your tiny house won’t be automatically fitted with a freshwater tank; you can choose the tank that fits best for your household.

Things To Consider:

• Before buying a tank, find out how much your house consumes a day on average. Include your drinking, flushing (if you have a regular toilet), dishwashing, and washing machine needs. 
• Keep your freshwater tank inside your tiny home. Like pipes and other plumbing accessories, it’s best to have it tucked inside to protect it from freezing or contamination. 
• Place your freshwater tank in a central location so it’s more accessible when hooking it up to the toilet, shower, and sink. Most homeowners store their fresh tank under the kitchen sink or halfway between the kitchen and the toilet. 

Greywater 

The greywater tank holds dirty water from washing dishes and showering, excluding human waste. There’s no need to purchase a large greywater tank if you can empty it out regularly. For a one to three-person house, a 35 to 100-gallon tank is already sufficient.

Even when being fully off-grid you would only have to empty out your greytank one to two times during a one-week period with these capacities. Of course, this ultimately depends on your level of usage and how frequently you want to empty your tank.

Like blackwater, grey water tanks are supposed to be emptied out in designated dump stations only. National parks, truck stops, and RV parks have sewage lines where you can empty out your greywater. 

We recommend switching to biodegradable products and using a smaller grey water tank (15 to 45 gallons). We’ve met tiny house owners who dispose of their greywater responsibly without going to dump stations since they’re using eco-friendly soap products. 

Blackwater 

Black water tanks hold human waste. In RV standards, the black tank would typically be the smallest one out of the three. It helps to have a small tank to keep maintenance easier. Since you’re emptying it out regularly, it becomes easier to clean and manage when you’re on the road. 

Unlike greywater tanks, blackwater has to be dumped in an official dumping area. There are local services that can also unload it for you, if you don’t want to deal with your black tank. We recommend getting a tank no bigger than 30 gallons. This will motivate you to empty it out more frequently and mitigate any leakage or contamination issues. 

Things To Consider:

• When choosing your next parking spot, always factor in a dumping ground. You want to be near a dedicated dump station whenever you travel so it’s more convenient to empty it out. 
• When emptying out your black and grey tanks, flush out your black water first. Then flush out the greywater so its contents can flush out residual black water. 
• If you don’t want to deal with emptying out your black tank, you can switch out your standard toilet to a composting or incinerating toilet.

Water Filter

The water filter is an important component of the plumbing system in your tiny home. As you travel, you won’t always have access to clean city water. Well water and campground water won’t have the same standards as city filtration, so it’s best to equip your tiny house with a reliable filtration system. 

There are two types of filter we would recommend:

• Inline filter
• Canister filter

Inline filters are attachments you can put on your fresh water hose. If your tiny house already has filtration systems in place (ex: if you have a filter on your faucet), this small water filter adds another layer of defense against debris and harsh minerals. It’s easy to use and incredibly affordable. 

Canister filters are great for full-time travelers. There are two types of canisters: standard canisters that you can customize or bigger canisters with a filtration system already in place. We recommend using a two-canister filter water system to remove sediment and address taste and odor issues.

Regularly emptying out your freshwater is crucial in preventing bacteria build-up. If you need to store freshwater for more than a week or two, we recommend using canisters with a CBC-KDF filtration system; this prevents bacteria growth even when water is stagnant. 

Inlet

The inlet is where freshwater enters your tiny home, to either fill up your fresh water tank or provide water to your fixtures.

Some tiny homes have two inlets; one to fill water directly into the tank, and another one to receive pressurized water (when connected to a supply line) that will be distributed directly throughout the fixtures. Other tiny homes just have one inlet and use valves to control where the water goes. 

We recommend using a pressure regulator to control the water pressure when filling up your inlet. We’ve heard stories of inlets breaking because of water pressure that was too strong. Having a regulator will give you better control of the water supply, and protect your plumbing structure from unwanted leaks.

Hot Water Heater

Just because you’re living in a tiny home doesn’t mean you have to give up hot water. Tankless water heaters have long been a staple in RVs, with so many models compatible for full-time tiny house living.

Traditional RV-friendly water heaters are run with propane, which is a fantastic option for off-grid living. The downside is that you have to install it outside your home and monitor it to prevent your heater from freezing. 

Their electronic counterparts work just as well. They can be installed indoors and provide reliable temperature control. They’re usually lightweight, have a small footprint, and are easy to install. 

For instance, the EcoSmart Eco27 tankless hot water heater is great for tiny homes with families. It has a unique power-saving feature that only limits power usage when water is flowing. More importantly, it can provide hot water simultaneously to two fixtures, which is perfect for a bigger tiny home.

We talk about other awesome tankless water heater options in our previous post: Top 5 Tankless Water Heaters for Tiny House Living. 

Drain

The drain is just the opposite of the inlet. This is where you connect your tiny home to the available septic system. If you’re off the grid, this is where you hook up your grey and black water tanks. 

Before emptying out your grey and black water tanks, make sure that your fixtures are secured around the drain. You can use the same hose to drain out the grey and black water tank. When emptying these out, we recommend that you put pressure at the depositing end of the RV hose (by putting your foot there or simply watching over it) to keep it from getting dislodged as your hose empties out the waste. 

Even campgrounds with a proper drainage system will require that you use your own hose when dealing with wastewater. Store the different ends separately and avoid letting these touch to prevent contamination. Don’t make the mistake of leaving your drainage hose outside during winter; the waste matter might freeze and congeal, making it harder to clean.

Choosing The Right Tiny House Bathroom Fixtures

Shower and Sink 

There aren’t unique considerations to make when choosing your shower or sink. These are the two plumbing fixtures that would function similarly to ones you’d find in bigger homes.

If water conservation is a priority, you can install low flow fixtures in your tiny home. Traditional flow rates for a shower fixture is about 2.5 gallons a minute. This might not look like much, but it can easily add up to 40 gallons a day for just a typical 15-minute shower. If you want to conserve more water, you can choose low flow fixtures that will help you reduce your water usage. 

Toilet 

There are three most popular options when it comes to the tiny house toilet. For tiny houses built on a foundation, being hooked to the supply line and a functional septic system means you don’t have to worry about where your waste goes. But for tiny house owners who are on the road, going to the bathroom might pose some challenges. 

When blackwater tanks and regular toilets feel like too much work, there are two waterless options to choose from: 

• Composting toilet: The compost toilet is probably the most popular alternative to the flushing toilet. It’s perfect for off-grid living because you don’t have to keep thinking about your black water tank. Your waste falls into a compost pile and decomposes for a period of time. To empty it, you can simply create a compost pile within your area so you can dispose of your waste responsibly. 
• Incinerating toilet: The incinerating toilet is a top-class option for tiny houses. Like the composting toilet, there is no water involved and no blackwater to worry about. The only downside is that incinerating toilets can be expensive ($3,000 to $4,000) but they’re worth it if you don’t want to do any work at all. When you flush, the waste falls into the incinerating chamber and immediately turns into ash. There is essentially no clean up required. 

Bathtub

As for the bathtub, it’s definitely possible to fit a bathtub in your tiny bathroom. Choosing the right bathtub is just a matter of smart placement: choose one that fits your existing space or find ways to hide it so it doesn’t eat up your already limited bathroom.

Read more: Best Bathtubs for a Tiny House. 

Tiny House Plumbing Made Easy 

Think of your little home’s plumbing as a package: you figure out the individual pieces based on your needs and create a system that works best for you and your family. 

The first step to figuring out the plumbing set up for your tiny home is to estimate your average water daily consumption. Consider if you are willing to deal with a black water tank or if you’d rather work with a composting or incinerating toilet. After you make a decision on these two factors, figuring out the rest will be a no-brainer.