How to Make Rainwater Safe for Use
In our last rainwater harvesting blog, we explained why untreated rainwater isn’t always safe for indoor use. But don’t worry, there are rainwater treatment options available to treat and use rainwater safely. In this post, we’ll guide you through simple treatment methods based on how you plan to use the water.
Whether you’re flushing toilets, doing laundry, or watering plants, there are steps you can take to improve water quality and protect your plumbing, appliances, and health.
Basic Rainwater Filtration – What Everyone Needs
Before using any harvested rainwater, even for gardening, you should have a few essential rainwater filtration components in place:
- Gutter screens or tank inlet screens
These stop leaves, sticks, and other debris from getting into your tank. - A first flush diverter
This redirects the first bit of dirty water from your roof away from your tank. It can be manual or automatic. - Mosquito-proof screens and tank covers
All unused tank openings must be closed. If the pipework is such that the pipe from the roof doesn’t drain completely after use, make sure to fit screens to prevent it becoming a breeding ground for mosquitoes etc. These also help keep insects, geckos, frogs, and other small animals out of your tank.
These basic features improve the water quality right from the start and help reduce contamination inside the tank.
Using Rainwater Indoors – Toilet and Laundry Supply
If you plan to use rainwater for toilets or laundry, a few extra steps are important to protect your pipes and appliances and keep the water fresh. For this, a separate pipe must be laid to the toilet and/or waterpoint where the washing machine is connected, not through the house mains.
For Toilet Flushing
- Keep the tank water clean
Add a sanitising agent like chlorine. A pool floater with slow-release chlorine tablets works well for this. Just be careful not to overdose it. - Use non-metal pipes and fittings
Rainwater is slightly acidic and can damage copper or metal pipes over time. Use plastic or PVC pipes instead. - Install a fine mesh or disc filter
This catches small particles before they reach your toilet cistern, helping to prevent blockages or staining.
For Laundry Use
- Same setup as toilets, with one big difference
Chlorine must be used sparingly. Too much chlorine in the water can bleach or damage your clothes. Aim for low levels – just enough to sanitise the water without affecting fabric. - Make sure the water is clear
Dirty or discoloured rainwater can stain clothes. A working first flush system and a clean tank are essential.
A Quick Recap
- Always start with good roof and gutter hygiene.
- Use screens, filters, and diverters to keep dirt and bugs out.
- Treat the tank water if you’re using it inside the home.
- Avoid metal pipes as they won’t last with untreated rainwater.
- Keep chlorine levels low for laundry to protect your clothes.
Rainwater harvesting doesn’t have to be complicated or expensive, but it does need to be done properly. With a few simple precautions, you can make the most of your stored rainwater and use it safely around your home.
In our next blog, we’ll explore more advanced treatment methods, including filtration systems and UV sterilisation, for those who want to go a step further.
