How-To plumb a Tiny House

by andrewodom on July 11, 2011 · 12 comments


Let me preface my full post by saying we have not yet plumbed our tiny house. In fact, we haven’t even begun the external build because…well, because of a number of small factors. With that said, I can add that I have spent much time talking about plumbing options, reading up on the subject, looking at “sticks-and-bricks” plumbing as well as RV plumbing options. The only parameters in plumbing a tiny house are truly the ones you place on yourself. You can go a number of ways which I hope to outline in the next few paragraphs.

The argument I have seen most is this.

Normal flush commode -vs- compost toilet.

The normal flush commode comes with a few stumbling blocks. Among them are:

  • Securing a plumbing permit
  • Plumbing inspection
  • Access to sewer or septic system
  • Plastic, sometimes toxic materials such as PVC
  • Need for a licensed plumber

The upside is that flush toilets seem to be safer. They are cleaner for the more conservative among us. The problem is they cost a lot more to install (consider the pipes). And yes, they are totally possibly in a tiny house, methinks.

Composting toilets on the other hand are becoming far more popular and in most cases look just like traditional flush commodes. They can be DIY projects costing little to no money. However, these DIYs tend to smell, allow the “floating” of fecal matter, and require regular cleaning/maintenance. The more high end composting commodes are available in electric and non-electric models, look almost identical to traditional flush commodes, and are quite clean!

Let’s get a little more in depth though in regards to traditional plumbing, shall we?

Fresh water supply. RV fresh water systems are typically designed to work with both a fresh water holding tank as well as a fresh water input when available. The holding tank can be mounted under the floor and remain largely out of sight. There is an input for filling the tank that is separate from the fresh water input for the system. The fresh water input has a garden hose style connection. 99% of RV stores sell hoses that are rated for potable (drinkable) water. There is also a 12 volt on-demand pump that can pump water from the fresh water tank when there is no water supply to connect to with the hose. This pump typically has a manual on/off switch that the user turns off when they connect to a fresh water supply by hose. The pump also tends to act as a one-way valve to keep water from the hose supply from getting back into the fresh water tank and flowing out the tank input. When the power connection to the pump is on and you turn on a faucet the pump senses the drop in pressure and turns on to supply water. RV systems have a pressure regulator on the hose input side to protect against uncertain pressure at RV parks and in rural water situations. Systems typically have water filters of various types that can be purchased at most RV and camping supply stores.

Fresh water plumbing. I had not heard of any plumbing other than copper or PVC until about two years ago. It was then that I found out about PEX tubing and I think it is a perfect option for tiny houses as it has the ability to bend and shape according to your interior dimensions. I would recommend (and we will use) 1/2″ PEX (ross-linked polyethylene) tubing including crimp connectors. They are easy to find at box stores and are inexpensive so they won’t destroy the budget. The fittings are brass. What I find most conducive about PEX is that it is very flexible, it is color coded (red for hot and blue for cold) and they fit nicely in the cavities of your studded walls.

Drain plumbing. Plumbing for sinks and showers can be pretty much the same as in a regular house. In that vein I would recommend 1-1/2″ black ABS pipe including sink and shower traps. Be careful to wrap any exposed plumbing though to keep it from freezing up during inclimate weather.

Holding tanks. In the RV world there are typically two holding tanks; black water and gray water. The reasoning for two is because in some camping situations there may be an option to drain off some of the gray water. In our current living situation we use homemade, non-toxic and bio-degradable cleaning and wash products so we use a simple leech system in which our grey water drains right into the soil via gravel and clay. There is nothing fundamentally wrong with having just one holding tank though depending on what you are going to do with the contents. Some RV’s dump their tanks by gravity while other use a special type of pump called a macerator pump. These pumps can be built into your tiny house or they can be portable. They are typically 12 volt pumps too. The advantage of using a pump is that they are capable of pumping the waste water through a garden hose for distances of up to 100 or more feet. They of course can also pump up hill. All of the information – while referencing RVs – can be custom fitted to your tiny house (a homemade RV, if you will.)

Toilets. There are basically two types of toilets you can use in a tiny house. One type is typically mounted directly above the holding tank and has a trap door sort of mechanism that drops waste directly from the toilet bowl into the tank when the toilet is flushed. The second type of toilet has a pumping mechanism that allows the toilet to be remote from the holding tank. There are models available with manual or electric pumps and there are some that work by vacuum action. One distinct advantage of these types of toilets is that they can flush up hill. This means that your holding tank would not need to be lower than the toilet.

Hot water heating. Tiny homes are curious in that some people employ very small, electric, hot water heaters while others prefer larger, propane powered systems. Most tiny homes generally have small tank type water heaters with a tank capacity of 6 to 12 gallons. Tank types are, of course, available for propane, electric or both. There is a large variety of smaller volume tank-less type water heaters available at most box stores (including our current one) that I think would be great for a tiny house.

Hot water heaters are beyond basic plumbing though and If you want to read about choosing a hot water heater you can read more at this link.

  • Anonymous

    Great post, really informative!

    • anotherkindofdrew

      Thank you for checking us out!

  • Dennis

    Shower water heaters:  We stayed in a cottage in Belize that had an electric heater right at the shower head.  The flow was low, but it was a very low tech solution.  Why aren’t they available here??  Well, they are.  Several similar ones are on Ebay;  one like we had in Belize for $35 (well, that’s the no reserve bid) and several nice ones for abut $100.  One has both a shower head and a kitchen hose sprayer that could be plumbed through the wall to the kitchen sink.

  • http://www.facebook.com/profile.php?id=576916498 Andy Hawkins

    Is anyone using any kind of solar hot water on a Tiny House?

    • anotherkindofdrew

      Not on a tiny house trailer. At least not that I know of. The reaosn being is because of the weight usually associated with a solar hot water heater as well as the space needed.

  • nw1911guy

    What about incinerator type toilets?

    • http://www.tinyrevolution.us/ anotherkindofdrew

      I have absolutely NO experience with them. I have actually never even seen one so while I would love to write about them I just don’t feel qualified to. I am sorry nw1911. Thank you for asking though!

  • http://www.facebook.com/profile.php?id=48506456 Kate Madorsky

    check out  http://www.thegreenerhome.com/index.php/105
    there’s a great write-up about the Enviro Loo. it’s an evaporation/dehydration system that is PRETTY cool! now i just have to figure out if it’s legal in PA… and/or how to make it so if it’s not!

  • Abel Zyl Zimmerman

    Around here, everybody seems to use the 5 gal bucket composting toilets. They are easy to use… and work really well.

  • Allaboutmaintenanceandrepair

    I’m a plumber and I would not suggest using the crimp style pex because the
    Fittings tend to leak if flexed or vibrated. I do recommend pex but, use a brand
    Like uponor pex http://www.wirsbo.com/en/Misc/Applications/PEX-Plumbing.aspx
    I am currently gathering materials to build my first tiny house and I plan on having a
    A full kitchen with a washing machine and dishwasher. In my bathroom I will have a
    Conventional toilet with a sink on top to wash hands with the flushing water and a 32″
    Shower. Thanks for the article. It is informative and gives options most people wouldn’t
    Know about.

  • http://www.facebook.com/people/Robert-Weiss/1092551763 Robert Weiss

    Toilets: Major miss- I N C I N O L E T Toilets

  • Pingback: Tiny House Plumbing 101: The Research Phase | TinyHouse43.com()

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