A water butt is one of the simplest and most cost-effective ways to make your garden more sustainable. You save tap water and money – and your plants love soft rainwater far more than hard mains water.
Which Water Butt Is Right for You?
| Type | Capacity | Price | Best for |
|---|---|---|---|
| Standard water butt | 200–300 L | €25 – €80 | Small garden, patio plants |
| Large water butt | 500–800 L | €80 – €200 | Medium-sized garden |
| Slim / slimline tank | 300–1,000 L | €100 – €350 | Space-saving, beside the house |
| IBC container (used) | 1,000 L | €50 – €150 | Large garden, vegetable plot |
| IBC container (new) | 1,000 L | €200 – €400 | When food-safe quality required |
| Underground cistern | 2,000–10,000 L | €1,500 – €5,000 | Complete rainwater harvesting |
Materials Overview
| Material | Approx. Cost |
|---|---|
| Water butt (300 L) | €40 – €90 |
| Downpipe diverter/filter | €10 – €30 |
| Overflow hose (per metre) | €2 – €5 |
| Non-return valve | €5 – €15 |
| Tap (watering can filler) | €15 – €40 |
| Butt stand (50 cm height) | €20 – €60 |
| Pump (submersible, 400W) | €40 – €120 |
Step-by-Step: Connect a Water Butt
Step 1: Choose the Location
- Position next to a downpipe (the pipe that carries rain from the roof)
- On level ground – a full 300L butt weighs 300+ kg
- Ideally on a stand: this allows you to fill a watering can easily from the tap
- A shaded spot is preferred – reduces algae growth
Step 2: Set the Butt on a Stand or Plinth
- Lay paving slabs or a purpose-made stand (min. 50 cm high)
- Check it is level with a spirit level
- Place the butt – get help for large tanks
Step 3: Install the Downpipe Diverter
The diverter directs water from the downpipe into the butt. When the butt is full, water passes back into the downpipe.
- Mark the height on the downpipe (approx. 30 cm above the butt lid)
- Cut the downpipe with a jigsaw or saw
- Fit the diverter – most use push-fit connections
- Run the hose from the diverter to the butt
Step 4: Install the Overflow
When the butt is full, water must have somewhere to go.
- Connect an overflow fitting near the top of the butt (usually pre-fitted)
- Run the overflow hose away from the house into the garden or to a second butt
- Overflow must be BELOW the inlet (otherwise the butt won’t fill completely)
Step 5: Cover and Mosquito Protection
Standing water = mosquito breeding ground.
- Ensure the butt has a lid
- Cover the inlet with fine mesh (max. 1 mm mesh size)
- Alternative: plant lavender nearby – natural mosquito repellent
Step 6: Install a Garden Pump (Optional)
For a large garden or IBC container a pump is practical:
- Lower a submersible pump into the butt
- Run hose or pipe to watering points
- Fit a pressure switch for automatic operation
Linking Multiple Butts
For extra capacity, link butts in series:
1. Run the overflow from the first butt to the inlet of the second
2. Use height difference: first butt higher than the second
Common Mistakes
| Mistake | Consequence | Solution |
|---|---|---|
| No lid | Mosquito breeding, leaves in water | Always fit lid and fine mesh |
| No overflow | Butt overflows, damage to house | Always install overflow |
| Butt on unstable ground | Tips over when full (dangerous!) | Stable foundation/plinth |
| Not draining in winter | Frost splits plastic butts | Empty before first frost |
FAQs
How much water will I collect?
Per m² of roof area and 10 mm of rain = 10 litres. A house with 80 m² of roof area and 600 mm annual rainfall = 4,800 litres per year.
Can I use butt water on vegetables?
Yes, rainwater is ideal for vegetables. It is softer than tap water and contains no chlorine.
Do I need to empty the butt in winter?
Yes, in freezing conditions. Water expands when it freezes and can split plastic butts. Empty the butt and close the inlet before the first frost.
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