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Tiny House Toilet Plumbing Explained (2 Important Differences)

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Tiny house toilet plumbing explained (composting toilet)

Tiny house owners have many different options when it comes to the types of toilet they can use.

To decide on which toilet type and model is the best fit for you, you must consider tiny house toilet plumbing, dimensions, design and cost.

In this article, we take a look at the different options we’ve found for tiny house toilet plumbing, where waste goes in a tiny house and how it is taken care of depending on your wether you’re on-grid or off-grid.

Disclaimer: This article does not contain any legal or professional advice. For advice tailored to your situation, contact your relevant authorities. For any decisions that impact the safety and well-being of humans please always seek advice from professionals. 

Table of Contents:

How do tiny house toilets work?

Key terms

  • Flush toilet: A toilet that uses water to flush waste to a separate location for disposal.
  • Dry (flush) toilet: A toilet that disposes of waste simply without the use of water to flush it away.
  • Composting toilet: A type of dry toilet that disposes of waste by the process of composting (biologically breaking down waste).
  • Incinerator toilet: A toilet that disposes of waste by burning it at high temperatures. 
  • Blackwater: Water from a toilet that may have come into contact with faeces. 
  • Septic tank: An underground chamber where sewage flows for basic treatment.

Tiny house toilet plumbing explained

A flush toilet in your tiny house will require the most plumbing by far. To be able to use one, you will need to connect it to a sewer system or septic tank to dispose of its blackwater. 

If you don’t have a flush toilet and instead decide on a dry toilet, then only minimal or even no plumbing is required. 

For flush toilets especially, your water supply and connection will determine your tiny house plumbing.

We’ll cover the key differences between tiny house toilet plumbing when you’re both on-grid and off-grid. 

Tiny house on-grid toilet plumbing

On-grid flush toilets

Some people ask whether you can have a flushing toilet in a tiny house. 

And the answer is yes, tiny houses can have flushing toilets. 

However, due to plumbing requirements, flush toilets are only really cost-effective if you plan to live permanently on-grid.   

This is because to operate a flush toilet in your tiny house, you must be permanently on-grid and connected to a sewer system or septic tank.

If you want to move around to other on-grid locations, disconnecting and reconnecting your toilet plumbing may be tricky.

A few other reasons why you may want to live permanently only on-grid with your flush toilet are:

  • If you don’t have access to a mains water supply, septic tank and/or sewer system, then you will need your own septic system.
  • Living off-grid could mean your water intake is limited. Being on-grid means you don’t have to worry about this.
The toilet in the Loft tiny house. This flush toilet uses traditional tiny house toilet plumbing.
Toilet in the Loft Tiny House by Mint Tiny House Company.

On-grid macerating toilets

Another toilet that is available for tiny house owners is a macerating toilet. 

This is where waste is churned and broken down before it is flushed away into a septic system.

A couple of advantages of using macerating toilets in tiny houses are:

  • They work well with low water pressure, as less flow is required to flush the blackwater
  • Require smaller pipes and less plumbing material overall (space-saving)

They work the same was as flush toilets in tiny homes and hookup to an on-grid sewer system or septic tank. The key difference is they use electricity to churn waste so it passes through the tiny house toilet plumbing more easily.

Other options for on-grid toilets

Other types of tiny house toilet, such as dry toilets, composting toilets and incinerating toilets have no plumbing constraints. They can be used when you’re on-grid but come most in handy when off-grid as they don’t require water.

However, if you are on-grid, using electricity to power any fans used in some dry or incinerator toilets may be useful.

Tiny house off-grid toilet plumbing

Off-grid flush toilets

Tiny house flush toilets (either using water or dry toilets) can still be used when you’re off-grid. However, you must have your own septic/storage system and plumbing to capture and store blackwater. 

This sort of tiny house toilet plumbing may not be practical as it adds a lot of extra weight to your tiny house and most people would rather not have waste stored right next to their home.

If you do choose to have your own water storage system to send flushed waste, then this will need emptying regularly at the nearest dumping station. 

When you’re off-grid, having a flush toilet may use too much of your precious water and electricity…

Flush toilets tend to use between one and three gallons of precious water per flush. Furthermore, dry toilets that suck waste using fans or air pressure may require electric hookup.  

The toilet in the Loft #2 tiny house. This flush toilet uses traditional tiny house toilet plumbing.
Toilet in the Loft Tiny House by Mint Tiny House Company.

Off-grid macerating toilets

Off-grid macerating toilets work in the same way as they do when on-grid. Since you don’t have access to a sewer system, like flush toilets, waste will have to be flushed into your own septic system. 

If you are planning to use your own septic system, a macerating toilet may be more desirable than a flush toilet.

This is because churning waste before it is flushed means your tiny house bathroom requires less plumbing and, in theory, will push waste into your septic system more easily. 

However, to churn waste in the first place, you need to provide your macerating toilet with electricity. Consider whether this is your off-grid electricity capacity can handle this. 

Off-grid toilet plumbing

The most popular off-grid tiny house toilet plumbing option is…

No plumbing at all.

Both composting and incinerator toilets require no plumbing. They don’t use water to dispose of waste.

Composting toilets store and break down waste that can be removed without the need for flushing. Incinerator toilets also store waste locally and can be emptied without the need for flushing it further away.

However, there are options to be able to add tiny house toilet plumbing to your composting toilet. If you do not want to store waste in the compartment below the toilet seat, waste can be directed away to a composting chamber that is separate from the toilet itself.

By separating your composting toilet into two parts, you can place the toilet in any place in your tiny house and then connect it via plumbing to the composting chamber which can also be kept in any area of the house.

To effectively move the waste from your toilet to the composting chamber, you have two options:

  • Use air pressure to suck the waste into the chamber (waterless solution)
  • Use a water flush to move the waste into the chamber

Although the second option uses a water ‘flush’ to move the waste, it uses far less than a conventional flush toilet. 

Conventional flush toilets normally use at least 1 gallon of water per flush, whereas this method of composting toilet plumbing has been said to use less than 0.2 gallons of water per flush. 

Composting toilet in the Kahurangi Koinga Tiny House by Build Tiny

What happens to tiny house toilet waste?

Waste from a tiny house toilet is considered blackwater and must be disposed of properly, in accordance with the guidelines of your jurisdiction.

Tiny house toilet waste can either be flushed into a sewer system or septic tank if you hook up to them. It can also be flushed into your own septic system that you will then have to dispose of yourself. Or, lastly, it can be treated inside your tiny home either via a composting or incinerator toilet.

Next, we’ll cover exactly where waste goes in your tiny house depending on which tiny house toilet plumbing you decide to go with.

Where does poop go in a tiny house?

Depending on which type of toilet you use in your tiny house, poop will either be decomposed, incinerated, flushed into an on-grid sewer or your own septic system.

Here’s a list of where poop goes in a tiny house based on the toilet you have:

Tiny house water flush toilet waste

If you’re using a tiny house toilet that uses water to flush waste, the destination depends on which septic system you’re hooked up to. 

Water flush toilets either send waste to the sewer, an on-grid septic tank system or your own septic system that you will have to manage.

This is why most people using tiny house water flush toilets are permanently on-grid and hooked up to a water supply and sewer system.

Tiny house macerating toilet waste

Macerating toilets handle waste in a similar way to flush toilets. After processing it, they will send waste to either a sewer, on-grid septic tank or a custom septic system that will have to be managed.

Tiny house waterless or dry toilet waste

Waterless or dry toilets are also common in RVs as well as tiny homes.

They dispose of poop by either containing it in sealed containers below the toilet seat (that can be disposed of manually), or by sending it to a separate septic system (similar to a cassette toilet) using air pressure. 

Whichever place the waste ends up, it will have to be disposed of carefully from there.  

Tiny house composting toilet waste

In tiny houses with composting toilets, poop ends up in a composting unit to be broken down biologically. 

This composting unit can be directly below the toilet seat, or tiny house toilet plumbing can be used to divert it to a separate unit located away from the toilet. 

Either way, poop will be broken down in this unit safely and then have to be disposed of periodically. 

Tiny house incinerator toilet waste

In terms of waste management, tiny house incinerator toilets work in a similar way to composting toilets. 

Poop is disposed of in an incinerator chamber below the toilet and then it can be disposed of periodically.