Hooking Up Your Tiny House and ADU Plumbing to Your Main House

So, you’ve taken the plunge. You’ve decided to build some type of a tiny, livable, breathable space for either yourself or someone else. And, you’re building it on your property. That’s the first step, and congrats on that. Now, you may be wondering “what’s next?” Well, hooking up your tiny house and ADU plumbing to your main house may definitely be “what’s next.”

In all reality, there are many “what’s nexts” that you will be faced with through this journey. But, you’ll learn a lot and you’ll be unbelievably proud of your accomplishments.

When building a small, inhabitable space, there are many aspects to consider. Electricity, water and plumbing are generally at the top of the list. Without those, your inhabitable space quickly becomes uninhabitable. With that said, let’s talk plumbing.

This post is going to assume you are looking to hook up the plumbing of your tiny home or ADU to your main house. And, we will assume that means water and sewer.

Let’s Talk Basics…

Water coming from the shower, sinks and washer of your tiny house or ADU is considered gray water.

Water coming from your toilet that is holding pee, poop and toilet paper (gross right?) is considered black water.

The objective is to get those two types of waters out of your tiny house or ADU and out to your sewer hook up.

Simple right?

In theory, yes. But there is still some work to be done.

You will need to determine how many feet of run you will need (that’s the distance from where the water is coming out of your new and beautiful dwelling to your sewer out on your main dwelling).

Next, you need to determine how the water (gray and black combined) is going to get there. If your tiny house or ADU is on a hill in your backyard overlooking the majestic valley below, it’ll be easy. Why? Because “stuff” runs downhill and there’s no pumping that will need to take place to get it down there. 

However, (and this is definitely more of the norm), if there is no downward slope (meaning the land is flat), your waters will need a bit of help. This is where a sump pump comes into play.

What’s a Sump Pump You Might Wonder?

And are all sump pumps created equal? Nope. Not at all.

Here Comes Your Next Lesson.

IF… you are only taking grey water out of your tiny house or ADU (and this would mean that you’re using a composting toilet or you have another toilet somewhere close by that people will use), then you just need a basic sump pump.

What does THAT mean, you ask? A basic sump pump is “activated” when it begins to notice water backing up in the system. The pump kicks on and then pushes the water out of the pipe leading from the sump pump and forces the gray water out, down the pipes and out to your sewer hookup. Then “poof.” It’s gone. Fantastic, right?

So what if you don’t have a composting toilet and you have a traditional flushing toilet with water in it? That’s a bit more complicated, but the principle is exactly the same.

When dealing with lumpy, bumpy, black water, a sump pump, on it’s own, can’t push those solids through the pipes. It needs some help. So some genius somewhere along the line came up with a grinder that is at the bottom of a sump pump. It’s a wonderful thing and works like this.

When the solids build up at the bottom of the pump, the grinder kicks on and grinds the lumps down to a beautiful semi-smooth liquid that then the sump pump can kick out down the drain just like described in the other process. Again, the process is the same but with an additional step.

Now, On to The Water System

There are a couple of ways to get water into your tiny house or ADU from your main house. You can either hook up directly to your hot water heater and run the flex pipe (1/2” lines that are either red, blue or white) through your attic, down the side of your house and out to your tiny home or ADU. Or, you can run your flex pipe from the plumbing of an indoor faucet (generally a kitchen sink will work if it’s on an outside wall) out to your tiny house or ADU.

Those water lines will then be connected to a hot water system inside of your tiny house or ADU to ensure there is hot and cold water inside for showers, laundry, etc.

Another lesson, and this one is equally as important.

All lines are run underground. The plumbing lines (the black pipe) are run generally 12” underground (so get ready to dig some trenches) and the hot and cold water lines run inside of a black pipe underground. This black pipe acts as an insulation, if you will, to your two water lines.

When in doubt, ask questions from people smarter than you in the world of plumbing. Even if you hire someone to do the work, it’s important to know the basics so that you can understand the process when your plumber is doing the work. Of course, places like the Home Depots of the world can guide you. However, actual plumbing stores will offer a bit more assistance.

Again, congrats on taking on this project. You will be so proud of yourself when it’s all said and done. If you have questions, send me a message and I’ll walk you through it.

Let me know how it’s going and what process you’re using. Hooking up your Tiny House and ADU plumbing to your main house may now not be as hard as you thought.