You flush your toilet with drinkable water. Crazy, right?
Every day, perfectly clean, chemically treated water flows from your municipal supply straight into your toilet tank, and then vanishes with the push of a handle. Multiply that by every household in your city, and the scale of waste becomes staggering.
Toilets alone can use up to 27% of your home's water, contributing to rising utility bills, overburdened sewer systems, and unnecessary environmental strain.
But here's the good news.
If you're already capturing rainwater, or even just considering it, you've got a cleaner, smarter way to flush. By rerouting rain barrel water to your toilet (or potentially even your bidet), you're taking a powerful step toward sustainability, preparedness, and self-reliance.
Why Consider Rain Barrel Water for Indoor Use?
Toilets are one of the biggest water hogs in your home, quietly consuming 20% to 25% of total household water use.
Every time you flush, that’s 1.6 gallons of drinkable, treated water being used to move waste. This is water that had to be pumped, purified, and pressurized just to get there.
If that sounds wasteful, that’s because it is.
A single 100-gallon rain barrel, commonly used in backyard water catchment, can supply roughly 56 flushes. That’s nearly a week’s worth of toilet usage for a family of four, using water that falls from the sky. It’s free, abundant (in most regions), and requires far less infrastructure to access.
Bidets, especially electric or pressurized models, can also use several ounces to a few quarts per use, depending on the model. While not as water-intensive as a full toilet flush, they still rely on potable water, unless you take steps to reconfigure your water supply.
Benefits Beyond Savings
Switching to rainwater for indoor use isn’t just a cost-cutting strategy, it’s a small act with big ripple effects.
For starters, you help reduce the burden on municipal water systems, which are increasingly under stress during peak usage and storm events. Every flush powered by rainwater is one less strain on aging infrastructure, one less gallon that needs to be chemically treated and transported.
Then there’s resilience. When power or water utilities go down, whether due to storms, freezes, or grid issues, having a backup water source can make or break your comfort and sanitation. A simple rainwater system can keep your toilet operational long after the tap runs dry.
It’s no surprise that preppers, rural homeowners, off-grid builders, and sustainability-focused families are already ahead of the curve. They understand what many are just starting to realize: your roof can do more than keep the rain off. It can keep your bathroom running, too.
How to Use Rain Barrel Water for a Toilet Flush
The simplest and most energy-efficient way to use rainwater for flushing is through a gravity-fed system. Instead of relying on a pump or pressurized plumbing, these systems use elevation to create water pressure naturally. For every foot of vertical height between your rain barrel’s water line and your toilet’s tank, you gain roughly 0.433 PSI (pounds per square inch). So, an 8-foot height, like setting the barrel on a deck or a raised stand, gives you just under 4 PSI, enough to refill a toilet tank with a little patience.
The basic components are straightforward:
Rain barrel (preferably 55–90 gallons) with a tight-sealing lid
Food-grade hose or braided tubing rated for low pressure
Selector valve to switch between potable and rainwater
Overflow routing system to safely redirect excess water
Screens or first-flush diverters to filter debris before entry
The setup is compact, low-tech, and effective, especially when connected to a downstairs toilet or any fixture situated below your barrel.
Step-by-Step DIY Setup Guide
If you're reasonably handy and comfortable with basic tools, setting up a gravity-fed rainwater system is a weekend project, one that can save you money for years to come.
Choose the Right Barrel and Location: Look for a durable, food-grade plastic barrel with a bottom outlet. Position it on a raised platform (cement blocks, a porch, or a custom-built stand) to maximize gravity pressure. Ensure the base can support at least 700–800 lbs when full.
Install a Selector Valve: Use a garden hose splitter to connect your rainwater line and your municipal line to your toilet’s fill valve. This lets you easily switch back to potable water if needed, especially helpful for troubleshooting or in dry seasons.
Drill Through the Foundation or Wall: Route the hose through your wall or foundation using a masonry bit and seal the opening with silicone. Keep the hose runs as short and straight as possible to maintain pressure.
Use an Adjustable Fill Valve in the Toilet: Not all toilet valves work well with low pressure. Look for models with an adjustable float arm, which lets you dial in water levels more precisely under gravity-fed conditions.
Secure All Connections: Use hose clamps, Teflon tape, and proper fittings to prevent leaks. Overflow ports must also be routed away from foundations to avoid water damage.
What About Bidets?
Here’s where things get interesting, and a bit tricky. Most bidets, particularly electric ones or those with spray nozzles, rely on consistent high-pressure water, typically 20–80 PSI. Unfortunately, your average gravity-fed system just can’t deliver that.
That said, there are handheld bidet sprayers or non-electric models that operate at lower pressures and may work with a pressurized rainwater setup (e.g., a pump-assisted system). Some off-gridders have experimented with battery-powered pumps or bladder tanks to provide a consistent flow for bidets and even showers.
At AquaBarrel, we've been keeping an eye on this space. Frankly, the idea of a gravity-fed or hybrid bidet system is still an untapped innovation opportunity. It’s possible, but not plug-and-play, yet. If you’re thinking of using rainwater for bidet hygiene, be prepared to experiment, innovate, or wait for the next round of eco-friendly tech to catch up.
Is It Worth It? Final Thoughts on Using Rain Barrel Water Indoors
If you’re still on the fence about using rain barrel water to flush toilets, or even to power a low-pressure bidet, yes, it’s worth it.
For flushing, it’s a no-brainer. With a single 90-gallon barrel elevated just a few feet, you can reclaim water that would otherwise rush down your gutters and transform it into 56 guilt-free flushes. That’s not just smart resource management, it’s a personal stand against waste. Every flush saves money, eases pressure on your municipal system, and supports your home’s resilience in emergencies.
Now, when it comes to bidets, the answer is a little more nuanced. Most modern bidets require high water pressure, which means a simple gravity-fed system won’t work out of the box. But if you’re experimenting with handheld sprayers, pump-assisted setups, or you’re just a trailblazer looking to innovate? There’s potential here, and we’re watching it closely at AquaBarrel.
At the end of the day, this kind of system is perfect for the eco-conscious, the off-grid, the budget-savvy, and the everyday homeowner who’s tired of wasting clean water on something as routine as a toilet flush. With the right setup, it’s not just functional, it’s empowering.
Do you still feel stuck, frustrated, or simply unsure of what to do next. We’ve spent the last 20 years helping people just like you make the most of their rainwater, without overcomplicating it.