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 has been unusable on the lot for months simply because we have no permanent pressurized water connection. They 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 plan to build houses with on-board water that we fill up and remain off any water connection for up to a week at a time. We can do this either by a) building houses with elevated water tanks and gravity fed water (such as Jay plans to do), or b) building tiny homes with RV-like tanks and water systems (as Brian will do). In the latter case, we’ll also design the system to allow us to also hook up 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 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 propane tankless hot water heater. Many Tumbleweeds have a traditional water heater that heats a 6-10 gallon tank. Given space considerations, this seems quite a bit of wasted space- and also wastes gas or electricity to keep the water heated 24/7. There are RV-specific tankless water heater (such as the PrecisionTemp RV-500) that heat water ‘on demand’ (when you turn the faucet on), but these are made to replace RV hot water systems and are considerably more expensive. After much research I’m going with this very inexpensive, wall-mounted Eccotemp FVI-12-LP propane tankless water heater that is very compact and narrow (7”). Note that this requires 120 VAC to run.
- A 40 gallon greywater tank to store used shower and sink water.
- An Incinolet incinerator toilet, 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).
Design: The system will be plumbed according to the schematic below, minus the blackwater tank.
Below you can see a an un-plumbed layout of some of the basic system components without the tanks: water heater, pump, accumulator, water inlet.
When plumbing the system, the priority will be to make it 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. Also, as a plumbing minimalist, I quite like the idea of a single pair of hot/cold water valves that operate over the bath sink, with a diverter valve that then pushes water up to a showerhead (I can’t recall the source of the image below, but it gives the general idea.)
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.