*Updated Feb 2014*

Currently the majority of tiny homes are built to accept pressurized water hookup from a hose. Simple, but also quite limiting if the house is ever moved for a few days (or longer) to somewhere where there is no pressurized water hookup- a music festival, or, say, a vacant alley lot.  The Tumbleweed Fencl we had here at Boneyard Studios was unusable on the lot for months simply because we have no permanent pressurized water connection. Standard micro houses also require water for toilets, and then a sewage hookup to dispose of it- most inconvenient, and always a little gross.

So, for not much more $, we are building houses with rainwater collection systems, and on-board water that we fill up and remain off any water connection for up to a week at a time.  One can do this either by a) building houses with elevated water tanks and gravity fed water, or b) building tiny homes with RV-like tanks and water systems.  In the latter case, we can also design the system to allow hook ups to pressurized water if/when that is available. The essential components of this modified RV system include:

  • 40 gallon RV fresh water tank (available in many sizes from places such as the tank-depot). This should ideally be mounted within the building envelope (insulated area) to keep water from freezing- as should all piping. If this is not possible, there are a variety of electric RV water tank heaters available. It should also be mounted securely, as it will weigh over 320 lbs when full.
  • A greywater tank to store used shower and sink water.
  • A fresh water fill inlet to fill up the tank (unpressurized)
  • A fresh water fill inlet to fill run the system without the water tank (i.e. when pressurized water is available)
  • A water pump (we’re using this standard SHURflo 2088-422-444 2.8 Classic Series Potable Water Pump). Note that this is a pump designed to run off of 12 volts, but you can easily substitute a 120 VAC model.
  • An accumulator tank to reduce pump cycling and smooth water flow (such as this SHURflo 182-200 Pre-Pressurized Accumulator Tank)
  • A simple water strainer to pre-filter the water (such as the SHURflo 255-313 Classic Series Twist-On Strainer 1/2″ FPT x 1/2″)
  • Some one-way valves to allow city water to plug into the system without any manual switching of valves.
  • A hot water heater.  This can be a) a traditional small electric heater, such as the 2.5-10 gal Aristons, b) RV-specific (and pricey) tankless water heaters such as the PrecisionTemp RV-500, or c) residential tankless heaters such as the wall-mounted Eccotemp FVI-12-LP (note that this also requires 120 VAC to run).

Design: The system can be plumbed according to a traditional RV schematic, below, with a few caveats

  • No blackwater tank: at Boneyard Studios we’re using Incinolet incinerator toilets, which just uses an electric connection to dispose of waste.  So we don’t plan to have any water going to the toilet (and consequently no toilet plumbing, no blackwater to dispose of, and no blackwater tank to take up valuable space).
  • No hot/cold water mixing for shower.  Almost all small water heaters have temperature settings on them which obviates the need for a separate cold mixing valve- simply lining in the hot water directly to the shower is simpler and works great, just adjust the temp at the tank.  Also note that one may run an electric water heater for 5-10 minutes prior to a shower, and leave the heater off the remaining time (this is quite efficient, and allows one to run an electric water heater in an off-grid electrical system, such is done in Minim House).

When plumbing the system, consider designing to to be a) easy to drain, for when the house sits empty during winter, and b) keep pipes outside of the walls, tastefully exposed, so if they fail, they do not fail disastrously, and can be more easily repaired should any freezing ever rupture them.

Water Efficiency: water efficiency becomes much more important when not connected to pressurized water.  This Bricor 1 gpm low-flow model is one of the most water efficient showerheads one we’ve found (there is even a .55 gpm model, but at a rate less than .96 gpm, the tankless water heater does not click on- a widely noted tradeoff of tankless water heaters- always check minimum flow rates).  Bricor will even ‘tune’ the showerhead to match the water pressure your pump generates (in this case, 45 psi).  Bricor also seems to make the most water efficient faucet aerator on the market (.375 gpm).  At this rate, a 40 gallon fresh water tank would give 30 minutes of shower +  26.6 minutes of sink time.  It’s worth noting that this water efficiency is far superior to any RV on the market today, as they all use flush toilets and typically less efficient showerheads/aerators.  Also note that one of the most water saving devices we’ve come across are the foot pedal water valves, available at restaurant supply stores. These valves are incredibly convenient, more sanitary, and much more water efficient than standard faucets- highly recommended.

**Also see the post off grid water for micro homes**

Category:
Brian, Design, The Houses, Utilities/City Code
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Join the conversation! 16 Comments

  1. [...] festival, or, say, a vacant alley lot.”Read how they are building an off-grid set-up at Boneyard Studios. /* */ nRelate.domain = "www.tinyhouseliving.com"; var entity_decoded_nr_url = [...]

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  2. Great ideas, plan to use some of them for my off grid tiny house!

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  3. Just a couple of comments: While your planned system will allow you to be away from a pressurized water system for up to a week, that Incinolet toilet requires 1.5 kwh of electricity every time you turn it on. So you either have to have access to shore power, or you need a fairly substantial alternative electrical system to run it. (We considered one for our off-grid homestead, but the electricity requirement was too great for our system.)

    While an RV shower head is not “low flow,” it is designed to save a tremendous amount of water, in that it has a shut-off valve on the side of the shower head. Rather than running the water the entire time you are in the shower, you shut the water off while shampooing, lathering with soap, etc. My husband and I can both shower without running the 6 gallon water heater out of hot water using this method.

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    • Thanks for your comments Debra. We also considered the electric use of the Incinolet. The thinking is that we’re ever far from a plug (out of urban areas, etc), a simple compost toilet could replace the Incinolet (such as the one many folks mention in the Humanure Handbook). That said, we’re going to see what a 1kW solar array can power on one of the tiny homes…

      On the RV showerheads, very true that technique is as important as function. On the latter, I found some even more water efficient showerheads, including the Bricor B-100.55 gpm model:
      http://www.bricor.com/water-saving-products/showerheads/

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      • We’ll be interested in seeing what that 1kw solar array includes, and costs.

        I’ve experienced “low flow” shower heads in hotels in the past, and was never satisfied with them. I always felt I needed to turn it up more or something. The way we use our RV shower, I don’t have that problem.

        Our RV is equipped with a control panel next to the door. This is where one finds the sensors that (sort of) give the levels for the batteries and the three water tanks, as well as switches for the accessories–water pump, electric water heater, propane water heater, lights and the awning and slide-out section. We turn the water heater (propane, since we’re off-grid) on when we need it and off when we don’t, to save propane. It takes very little time to heat up, so it’s the next best thing to an on-demand water heater.

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    • I used to live in St. Croix U.S.V.I. and we had cisterns under our home that held all of our shower, commode, and sink water. We bought purified water to drink. Because of the need to save water, we had a shower head with an on and off lever on it. After living there for almost three years, my whole family became accustomed to using the lever for the shower. We continued to use one after coming back to our home in the states, but, eventually got used to avoiding it. I still like it for saving water. You get wet, wash, rinse. Not just once, but as many times at it takes. BUT, it definitely saves water! Lots of water!

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  4. Another alternative is using a camping portable shower setup. There are lots available, mostly using propane to heat the water and either a pumped up pressure system or a battery operated pump. There’s even a water heating coil available that goes in a campfire or on top of a stove. Just search for portable shower or camping shower and there are lots of hits. There are also portable greywater tanks on wheels that could be used by a house without it’s own drainpipe to be dumped elsewhere (properly of course!) If you have one house plugged in to water and sewer it should be possible to fill water tanks from it and drain greywater from other houses using it’s systems as long as you set it up to minimise “accidents”. If nothing is available onsite it’s always possible to set up a little trailer with clean water and greywater tanks to service tanks in the houses using offsite resources as long as you’re scrupulously clean about it.

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  5. I have long thought that builders of tiny houses should pay more attention to what is done with plumbing in RV’s and I think you are mostly right on with your plan. You might take note though of a couple of things that might be of use. You my not need separate one-way valves for example.
    1.) Standard RV water pumps have a built in one-way valve to prevent city water from flowing backwards through the pump.
    2.) Standard readily available RV city water inlet fittings most typically also have a one-way valve built into them. Sometimes they also have a pressure regulator in them to protect the system from too high water pressure.
    On another note there is an alternative to draining the water out of your system when stored during cold weather. I use it on my 1973 Airstream trailer. You can install a “Y” valve designed for this purpose on the fresh water tank side of the water pump. You can then attach a flexible tube that can be used to draw RV antifreeze into the water system with the pump. You just open your plumbing valves until the colored antifreeze comes out telling you that the system is full. RV antifreeze is non-toxic and does not harm your plumbing. In my system I use another RV accessory that allows me to connect an air hose to the city water inlet to blow the antifreeze out of my pipes when I am ready to put water back in. You can of course just flush it out with fresh water but I like to reclaim the antifreeze for use next year so the air helps let me do that without diluting the antifreeze so much.

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  6. Check into Marine Sanitation Devices. Several companies make these systems. They treat the grey and black water on boats to an acceptable level as deemed by the Coast Guard to then be discharged in to the lake/river/sea water. You can also recycle this water back into the system to illiminate dumping or holding in a tank. I don’t know the land applications, but if you can discharge into the lake, you might be able to discahrge on a land discharge field.

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  7. Thank you for the platform to post. It was a great read. In reference to your 40 gallon holding tank i just wanted to add to the list of available suppliers, and i hope you don’t mind me doing so. Plastic-mart really specializes in custom fitting sizes and locations. If you can put it on paper, they can pretty much get it done. Appreciate your time.

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  8. Thank you for this plumbing post – it’s the most informative that I have come across so far. My plumbing plans are the next step in my construction… I super appreciate all the product links and explanations of why you chose what you did. Thank you!

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  9. Very useful information…ur time is appreciated….I’m in the very early planning phases of living in a small home..doing my home work …thank u! Tammy lee

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  10. […] Boneyard Studios posted a very informative post about plumbing last year – you can read that here. […]

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  11. Thanks for sharing your ideas. I

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  12. […] I explored improvements to standard micro house water systems for water systems where there is no permanent pressurized water hookup or sewage line.   In many […]

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  13. […] found some great articles about plumbing a tiny house like these two HERE and HERE, but all the ones I found mostly focus on going all off-grid OR all pressurized. THIS […]

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