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Tiny House Rainwater Collection Options (Off-grid Water Catchment)

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Tiny House Rainwater Harvesting

Collecting rainwater can be a great way to help the environment and provide a backup or even main supply of water to your tiny house.

It can be used for many things in your tiny home and garden.

This article will help you decide if it’s worth collecting rainwater for your tiny house, how much you need to collect to meet your needs, as well as the methods you can use to collect rainwater yourself.

Is it worth collecting rainwater in your tiny house?

Rainwater can be used for a variety of different things in your tiny house.

As long as the water is treated appropriately, you can use it to flush your toilet, rinse, wash, clean, water plants and even drink.

For drinking water, you will need to ensure that it is sterilised and purified correctly, as rainwater can be dangerous if consumed straight after collection.

Before you consider rainwater harvesting for your tiny house, you also need to make sure that collecting rainwater is legal in your jurisdiction. Some parts of the U.S.A and other countries don’t allow individuals to do this freely.

Lots of tiny house owners collect rainwater for these purposes, especially if they’re settled in an off-grid location without access to mains water. Every little helps!

Some advantages to collecting rainwater as opposed to purchasing water or traveling to a spring or mains supply every few days are:

  • The water you collect is free
  • Your rainwater catchment system is cheap to maintain
  • The process is environmentally friendly

However, there are some set-backs as well, such as:

  • The water source is unreliable – you can’t choose when it’s going to rain
  • It requires effort to maintain
  • You need to have space for the water storage tank and for the system of pipes and gutters

Rainwater harvesting suits people whose tiny house is permanently off-grid in a fixed location. This means that they can use space outside of the house for rainwater storage and not have to worry about moving it. Gutters and outside pipes can be installed too if you’re not moving the house anywhere.

Will there be enough rainwater for your tiny house?

To answer this question, firstly you need to decide on the tasks (i.e. flushing the toilet and rinsing, or drinking and showering, etc) you are going to use rainwater for.

Then, you need to calculate your average daily water consumption for these tasks.

Here’s a list of how much water will be used for each one:

  • Shower: 1 gallon per minute
  • Toilet: 1 gallon per flush
  • Washing Machine: 11 gallons per use
  • Dishwasher: 2.2 gallons per use
  • Running tap: 1.3 gallons per minute

Next, you need to estimate whether you will be able to catch enough rain to fulfil these tasks, and whether your area receives enough rainfall to facilitate this.

To do this, use the following formula to estimate how many gallons of rainfall you will receive per month:

Area (in square feet) * Rainfall depth (in inches) * 0.623 = Gallons of rainfall harvested

The area is your catchment area, and you can use websites such as this one for the USA and this one for the UK, to gather rainfall depth data for your area.

Once you’ve calculated your water consumption and how much rainfall you expect to catch, you will know whether rainfall harvesting is feasible for you.

Do tiny homes need gutters?

If you want to harvest rainwater for your tiny house roof, then you will need gutters.

If you’re not interested in rainwater harvesting, or you have a different catchment system (barrels or tarps), then your tiny house does not need gutters.

Gutters are essential for collecting rainwater from your roof and sending it to a downpipe and into a storage tank, such as a cistern.

In addition to gutters and a downpipe, you will want to implement a pre-filter to make sure that debris doesn’t end up in your rainwater storage tank.

This can either be a flush tube or a screen cap.

A flush tube is a downwards pipe that will fill up first, before the excess water runs down a separate, more horizontal pipe into your rainwater storage barrel.

This means that any debris collects at the bottom of this flush tube. You need to ensure that this is emptied periodically so that the debris does not overflow and go into your rainwater barrel.

You also need to make sure that it doesn’t freeze in the colder months.

A screen cap is essentially a filter in the middle of your drain pipe. They are easy to install and require you to cut a gap in the middle and then fix the filter in between. The cap needs to be outside of the pipe so that debris can fall away and doesn’t cause a blockage.

Tiny House Gutters

How do you collect rainwater without gutters?

You can collect rainwater without gutters by using a different catchment system, such as rain barrels or a tarp.

Rain barrels don’t take up that much surface area, so you will need quite a few if you want to collect a substantial amount of rainwater. You don’t necessarily need a network of pipes, but you will have to manually transfer the rainwater from each barrel into your storage tank or cistern.

A tarp is a great way to catch rainwater. It’s essentially a large sheet that acts as your tiny house roof would, and uses a slope and gravity to send rainwater downwards into a barrel. You can set these up between trees, on top of outdoor belongings, or even attach it from the side of your tiny house.

How to store and use tiny house rainwater

Once you have collected your rainwater, it must be transferred to a storage tank for safe keeping until you need to use it.

Some people filter rainwater in their tiny house so that it is safe to consume. Make sure to check your local laws to see if this is legal for you to do so.

If your tiny house is in a permanent, fixed location and you have permission to use the land nearby, you can bury a cistern underground to store the water.

Again, check your local jurisdiction laws in case there are any preventing you from doing this.

You can also purchase rain barrels that sit above ground, outside your tiny house, and can store between 40 and 80 gallons of water each.

Alternatively, you can purchase barrels not specifically designed for this and add your own spigot and pipe.

If you’re wanting to pump water from your cistern outside, or from a rain barrel inside or outside, then you will need a tiny house water pump to do this.

These can even be hooked up to a solar power system, so every stage of your rainwater harvesting is free.