Tiny House Plumbing

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 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.  Alright, are you ready? Let’s dive into Tiny House plumbing!

Tiny House Plumbing

“Off-Grid” VS. “On-Grid”

Fresh water is the water you use for drinking, cooking, showering, toilet, washing dishes, etc. You’ll need to obtain fresh water by connecting to city water (on-grid) or filling fresh water storage in your tiny house (off-grid). I have both options in my tiny house, which I recommend for flexibility in parking. Of course, if you will always have an opportunity to connect to a hose and spigot, having an off-grid system is not necessary.

My “Off-Grid” fresh water system

First, let’s talk about my off-grid fresh water system. For water storage, I fill a 40 gallon water tank, which is secured within the insulated part of my trailer under my kitchen counter. I fill this tank by connecting a 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 a good I am not “average.” I use about 10 gallons of water a day. That includes the water I drink and use to cook, clean, shower and do dishes. When I am off-grid, I fill my tank every 4 days.

Our Water Inlet

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 generator or solar power when off-grid.

Our 12V Converter

My “On-Grid” fresh water system

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 fresh water tank or pump. 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.

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. 

Water pump

Grey Water – Water that drains out of sinks and showers

Grey water is not necessarily waste. I use biodegradable products for my soaps, shampoo, conditioner, lotions, etc. My grey water 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 grey water for irrigating my garden, similar to Art’s tiny house system. It’s a great way to recycle!

When I travel with my tiny home, I use a portable grey water tank or I connect to a campground sewer systems with a sewer hose.

grey water tank
Portable grey water tank

As with fresh water tanks, grey water tanks come in all shapes and sizes. Mine is only 15 gallons, so I 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 grey water 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 grey water 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 grey water.

*As a note, dumping grey water is not legal everywhere. Research your location and use your best judgement. 

Greywater drain and portable tank

Black Water waste water from a toilet

I don’t have this because I use a composting toiletNo, it doesn’t stink. I’ve spent a lot of time around boats, and I’ve witnessed first hand how black water is dumped. I can say with certainty that dealing with a compost toilet is 100% less disgusting than dumping black water. Plus, it requires zero fresh water to operate. I did plumb a fresh water line for a possible flush toilet addition in the future (in case I sell my house one day). You can see that above/behind my toilet in the below photo. Although, I don’t plan on ever using it.

I have a lot more to say about my toilet, but I don’t want to get hung up on poop in this particular article. Read more on our toilet here.

toilet thgj
Nature’s Head composting toilet

Sustainable water systems. Future Tiny House plumbing plans!

I have big plans for a more sustainable water system when I settle down somewhere. I’m very interested in building a large outdoor shower that is fed by a rain water collection tank. That tank would elevated above the shower (like a mini water tower), so the pressure would be powered by gravity. My water would either be heated by the sun or by a coiling pipe running through an elevated compost bin. In this scenario, I wouldn’t need a water pump or hose! More research is needed, but I often find myself pondering: How can I take a shower for free?

YOUR TURN: How did you handle Tiny House Plumbing?

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58 thoughts on “Tiny House Plumbing”

  1. Hello! How did you attach the grey water tank to the bottom of your house? I’m building an expedition vehicle and am having trouble finding a company that can recommend a product designed to be attached to the underside of the vehicle. Thank you

    1. Also, note that the portable grey water tank is not attached to the trailer. It’s on wheels so that it can be towed away and dumped easily. If you are looking to attach a tank to the underside of your vehicle, check out RV forums for their recommendations.

    2. Hi! I didn’t attach it. I have a rolling, portable greywater tank. When I move around I simply throw the tank in the back of my truck. I think it is better this way because if the greywater tank was attached, I would have to drive my tiny house to the dumping station every time I wanted to dump it. I’d rather disconnect the greywater tank and roll it to the dump station.

  2. i have a couple of questions about water going out of your house, i can see the PVC pipes under the trailer,

    1- are your sink and your shower connected to the same drain?
    2- is the drain all the way through the floor? through the flashing?
    3- how do you keep everything from freezing ?

    we live in Northern Vermont and temps can be -20 for days

    thank you
    we are about to build, and I am confused about setting up the plumbing drains

    we will have to be self contained in order for us to be legal where we want to park. The septic company has agreed to supply a temporary tank and come pump that out whenever we need, so will not have to deal with the grey water

    thank you,

    1. 1). Both the sink and shower flow into the same PVC pipe under the trailer.
      2). Yes.
      3). In the winter we skirt our tiny house, which helps a lot. You can also wrap heat tape our use heated hoses. We used out interior water tank for fresh water in the winter and would only fill the tank when the weather was warmest. Our spigot froze a few times. Our water heater froze as well. Explore this website for more cold weather prep, tips and stories. We’ve written about it in detail.

      Good luck on your tiny adventure!

  3. Quick question, are your freshwater drain tanks and grey water lines different lines or are you using the same line? Thanks!

      1. Thanks! A second quick question. I’m looking for the same 90″ you have that goes into your tank. Male threaded on one side, the other side connects to the vinyl hose. Do you remember what this is or where you got it? Thanks!

  4. Hey! Do you have p traps, if so where are they? Do you have grey water from shower and sink drain from same outlet? What did you use to attach the plumbing underneath the house? Did you do that yourself or hire out? It looks very legit underneath and solid, have you had any issues with clearance because of piping being under trailer? Thanks a lot you guys are awesome and huge help along our own journey!


    1. Our P-traps are under the sink and under our elevated shower (so the p-trap is in the insulated part of the house). Grey water goes to the same place. Plumbing was done by a plumber and by Guillaume. And we’ve had no issues with the clearance of our plumbing 🙂
      Thanks for your kind words and glad you like our project!

  5. Hi I am wondering what hose you used to connect from the gravity fill inlet to the water tank? I am about to do this on my own but haven’t been able to find any details on how to hook that part up, thank you!

  6. Hoping you guys can help us out with this: we’re building our tiny house now and have a utility shed that we’re hoping to use for a propane tankless water heater. It’s enclosed in the shed so doesn’t have open-air ventilation but also isn’t as well insulated as inside of our house (we live in Olympia, WA so it doesn’t get TOO cold here). Should we go with an indoor (that might need more insulation) or outdoor (that might need more ventilation) unit then???

    1. Honestly I’m not sure… It all depends on which water heater you use, they all have different characteristics, though most do need venting. If it does freeze, you might want to commit to an indoor heater just to avoid the freezing problems, unless it self-protects.
      They will all be slightly different, you’d get better information contacting the manufacturers directly, or a plumber. We’re not quite water heater specialists just yet 😉

  7. Hi Guys,
    I am in the middle of my build (24′ cypress) for my 8 year old son and I. I was planning to use the same water heater you had but have not ordered it yet. So I am wondering if you liked your water heater enough to replace it with the same model or did you decide to try a different brand or model?

    1. Yeah we would. The issue we had was human error and I feel that any other instant propane water heater would’ve failed before ours did. During the 3-4 weeks we were gone, the temperatures dropped down to the single digits and the pressure in our propane tanks dropped dramatically. The pressure wasn’t high enough for the water heater to light and protect itself against freezing, so it froze and broke. We replaced the part and ordered heated blankets for our propane tanks and it works like a charm now! If we wanted a tankless propane water heater for our next tiny house, we’d go with the same one.

  8. Hello again! I’m on to plumbing and am considering the same tankless water heater that you have. Have you had any issues with it? I also noticed they make a wall vented unit and the floor vented. Do you have an opinion one way or another on that option? I have a Tumbleweed trailer so floor venting would be similar to your trailer. Thanks!

    1. We just had an issue with ours because we left for a month and temperatures dropped to about 0 degrees F. Our propane tanks were pretty empty and with the temperature drop, our propane system didn’t have enough pressure to fire up the water heater so our heating element froze and busted. It wasn’t the water heater’s fault, it operated as advertised and tried to protect itself from freezing but our propane system lost pressure because of the cold temperatures did the rest. Any other tankless propane heater would’ve failed earlier. (we’ll probably write more about all this)
      We picked the floor vented one so we didn’t have to have a big hole in our wall.

  9. I filled my 46 gallon water tank up and then ran water over to my tankless water heater. I have a pump that looks exactly like the one you are using so my set up seems a lot like yours. Now the problem. After running the water over to the heater, I let it get warm but after 20 to 30 minutes the temp was only around 67 or so. Why isn’t the water heating up faster than it is? and there seems to be low pressure although I am using a pump that is just like yours. Is the pressure suppose to be very strong? Thanks for any input you may have.

    1. Hi Ed, I’m not too sure how to help you with this. We just upgraded to this silent water pump but they basically have the same flow (3gpm vs 2.9gpm). We use 3/8 pex piping and our shower head is a 1.8gpm. Not sure about our sink faucet but it’s probably less than that. If you don’t have the exact same water heater, I really can’t help you. We live at 9,600ft so our water heater only functions at 60% capacity or so (that happens with all propane heaters). That means we only get about 50 degree temperature rise. To make sure our water is hot, we open the hot water only far enough for it to trigger the heater, the slower the water goes through the heater, the hotter it gets. If you open it full blast on hot, the water goes quicker through the heating elements and doesn’t heat up as much. Our heater heats up in 5-10 seconds. As for the 20-30 minutes after, I can’t speak for it. We only use hot water for a few minutes, all of our showers are short showers. The water heater might have a timer to protect it from over heating after a while.
      Good luck

  10. How wide is your tiny house bathtub? I’m just now starting to plan mine and I’d really like a proper bathtub. Maybe a Japanese soaking tub. But I’m curious about typical/average tiny bathtub dimensions?

      1. Oh wow! That’s so tiny! I’ve been looking at tub options. I don’t know what I’m going to do yet. Thanks for taking the time to respond! I might just go with a shower.

  11. Great post! I don’t know if you have seen this but this is what I use. I got it online at Wayfair ( free shipping) and it works great.

    Blue Wave Products Poolside Solar Outdoor Shower

  12. What’s that black-box adapter you are using that connects your gray water drain to the gardening hose? Thanks for all the information, btw. I just finished plumbing my house and stole almost all of your ideas 🙂

    1. Are you talking about a vent to fill your water tank? The one we have is built into our water inlet… If you’re talking about a grey water tank vent, we have a dinky one inside and don’t like it. Your grey water vent should probably just go outside

  13. Thanks for an informative article. I realize you are talking about plumbing, but I’m wondering how you like your galvanized bathroom walls. I love the look and would like to steal your idea. Any problems so far? Any suggestions or something you would do differently?

    1. Honestly, no problem so far! It was fairly easy to work with. We used our leftover Grace Ice & Water Shield to make sure the backing is waterproof, that underlayment makes any water that’d make it behind fall into the tub. The galvanized steel will probably whiten over time and maybe rust in 10-20 years.

  14. The Natures Head composting toilet is excellent. We have used it as a family of four for the last four years at our homestead.

    1. We fill up before going off-grid. We usually can last 4-7 days depending on how many showers we take. We’d probably get a few jugs of water for drinking and cooking if we were to stay long. But we don’t usually stay off-grid for long.

  15. So complicated, and I’m nowhere near ready to think about that yet. Thank you for sharing! I am thankful that Jon re-plumbed his house with Pex under the supervision of a plumber, so he’s learned the basics. Framing, construction, angles, all that stuff makes sense to me — plumbing? Not so much! Glad we have time to research. I’ll be recalling this post when we’re closer to that stage of construction.

  16. Like you, we are extremely careful with our grey water discharge because we live on a lake. We even wipe all of our dishes before washing to make sure food particles don’t get into our discharge. We also use a compost toilet. It changed our lives! No more long hikes up the hill to an outhouse. I see you are coming to British Columbia on your tour, but it looks like you will bypass our location on the Sunshine Coast. I’ll be watching to see where you do stop and maybe we can come down to meet up.

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