How to Install a Rainwater Collection Water Butt

The Step-by-Step DIY Guide

The DIY Checklist:
What You’ll Need

Harvesting rainwater is a brilliant, eco-friendly way to keep your Irish garden lush while keeping water usage sustainable. With Ireland's high volume of annual rainfall, a water butt can fill up in just one heavy downpour. Setting up a water butt requires careful alignment with your existing downpipe, solid stabilization, and an airtight fit to prevent damp issues on your exterior walls.

Man holding a rainwater diverter/downpipe connector fitting.

1.

SAFETY
GEAR
(PPE)

Safety Glasses: Essential eye protection when drilling holes into the plastic water butt or using a saw to cut the gutter downpipe.

Work Gloves: Heavy-duty grip gloves to protect your hands from sharp plastic edges, metal burrs, and hacksaw blades.

2.

TOOLS &
EQUIPMENT

Hacksaw or Junior Hacksaw: Required to make clean, straight cuts through your home's plastic gutter downpipe.

Combi Drill or Impact Driver: For securing brackets, drilling hose connection points, and assembling the system.

Holesaw or Spade Drill Bit: Sized specifically to match your diverter hose (usually 25mm to 32mm) if the water butt does not have pre-drilled inlet ports.

Tape Measure & Spirit Level: Absolutely critical to align the diverter perfectly level with the water butt inlet.

Fine-Tip Marker or Pencil: To precisely mark out your downpipe cut lines.

3.

Materials, Fixings & Accessories

Water Butt (200L to 500L Capacity): A heavy-duty, UV-stable plastic barrel fitted with a tap at the base.

Butt Stand, Base or Stabilisers: Elevated base block to raise the butt off the ground, allowing you to fit a watering can directly under the tap.

Downpipe Diverter Kit: An inline downpipe connection piece with a flexible hose that channels water into the butt and automatically stops when full.

Leaf Filter & Mesh Top: Fitted on top or inside the diverter to keep autumn leaves, moss, and debris out of your clean water store.

Overflow Hose & Fittings: Redirects excess rainwater safely back into the downpipe or to a nearby garden bed when the system is maxed out.

Silicone Sealant & PTFE Thread Tape: Ensures a completely watertight seal around the tap, inlet connection, and overflow joints.

Top Tip: The Gravity Level Rule.

Your downpipe diverter MUST sit completely level with the maximum fill line of your water butt. If you install the diverter too high, the water butt will overflow from the top lid, rotting your wall. If you install it too low, the water butt will stop filling before it is actually full. Always use a spirit level between the diverter mark and the inlet hole.

Top Tip: A Rock-Solid Base.

A fully loaded 200L water butt weighs exactly 200kg, and a 500L model weighs half a tonne! Never place a water butt on soft grass, loose soil, or uneven gravel. Always lay a flat concrete paving slab or construct a level, solid timber platform as a foundation to prevent the stand from leaning or tipping over.

Step-by-Step DIY Installation Guide

STEP

01

Set Up and Position the Base

Prepare the Ground:

Find a flat, solid area directly adjacent to your downpipe. Clear away loose gravel or soil, and lay down a heavy-duty concrete paving slab.

Place your water butt stand or base flat on the slab. Check it in both directions with a spirit level to ensure it is completely horizontal.

STEP

02

Assemble the Water Butt Fittings

Fit the Tap:

Wrap PTFE thread tape tightly around the threads of the plastic tap (at least 5-6 rotations clockwise). Screw the tap firmly into the pre-threaded hole at the bottom of the butt. Tighten the interior locking nut, then run a small bead of exterior silicone sealant around the seam.

Install the Inlet Port:

If your water butt lacks a pre-drilled inlet hole near the top, use your combi drill fitted with a spade bit or holesaw (typically 25mm to 32mm) to drill a clean hole through the marked plastic profile.

STEP

03

Measure and Mark the Downpipe

Align the Heights:

Set the water butt securely on top of its base. Use a spirit level and straight edge running from the top of the butt's inlet hole over to your downpipe. Mark this point on your downpipe with a pencil.

Mark Cut lines:

Refer to your specific diverter kit instructions. Typically, you will need to cut out a small section (about 30mm to 100mm) of the downpipe. Mark the upper and lower cut boundaries directly on the downpipe using your level.

STEP

04

Cut the Downpipe

Secure and Cut:

Put on your safety glasses and gloves. Gently detach the lower downpipe brackets if needed to gain flex. Carefully use your junior hacksaw to cut straight through the downpipe along your marked lines.

Clean the Edges:

Use a utility knife or sandpaper to remove any rough plastic burrs from the inside and outside of the cut edges to ensure smooth water flow.

STEP

05

Install the Diverter and Connect Hose

Fit the Diverter Piece:

Slide the diverter unit onto the cut ends of the downpipe (top side first, then drop it down onto the lower pipe). Push it firmly into place to secure it.

Link the Butt:

Connect the flexible hose from the diverter outlet port directly into the water butt inlet port. If it's a tight squeeze, warm the hose ends in hot water for a minute to make the plastic pliable.

STEP

06

Set Up Leaf Guards & Overflow

Keep Out Debris:

Pop your leaf filter into the top opening or slide the mesh cover tightly over the main lid of the butt to prevent mosquitoes and gutter moss from contaminating your storage tank.

Secure the Overflow:

Attach an overflow hose to the opposite high-level outlet on the butt. Route the open end to a drain or directly into a nearby flower bed to manage excess water safely during heavy winter storms.

How to Install a Rainwater Collection Water Butt: Irish DIY Guide

Water Butt Installation Calculator

1. Define Installation Scope

Location Label

Qty (units)

Capacity (Litres)

2. Product Configuration Options

Downpipe Profile Shape:

Inlet/Diverter Type:

Overflow Hose Length (m):

Level Safety Factor:

System Setup Cross-Section View

Estimated Materials Required

Total Tank Capacity Target: 0 Litres

Water Butt Tanks (With Taps): 0 Units

Water Butt Elevated Stands: 0 Units

Downpipe Diverter Kits: 0 Kits

PTFE Thread Tape (12m roll): 0 Rolls

Silicone Sealant (Cartridge): 0 Tube(s)

Overflow Hose Required: 0.00 m

Mesh Top/Leaf Guards: 0 Units

Standard Rainwater Yield Specs:
• Water butt sizes: Standard domestic butts come in 200L, 250L, 350L, and 500L capacities.
• Diverter details: Standard kits are designed to clamp onto both 68mm round and 65mm square downpipes. One complete kit is required per water butt unit.

DIY Project Shopping Checklist

Rainwater Water Butt Installation Shopping Manifest

Calculated Project Scope: 0 Litres Total Capacity | Downpipe Profile: 68mm-round

1. Dynamic Calculated Materials & Core Basket Items

GOT IT	MATERIAL DESCRIPTION	TARGET QUANTITY REQUIRED
☐	Heavy-Duty UV-Stable Plastic Water Butt Unit (with base tap)	0 Unit(s)
☐	Robust Plastic Elevated Butt Stand / Base Module	0 Base(s)
☐	Universal Rainwater Downpipe Diverter Kit with connection hose	0 Kit(s)
☐	PTFE Thread Sealing Tape (12mm x 12m roll size)	0 Roll(s)
☐	Exterior Grade Silicone Sealant (Standard cartridge)	0 Tube(s)
☐	Flexible External Overflow Drainage Hose (per metre)	0.00 m
☐	Heavy-duty Mesh Top / Leaf Filter Guard Cover	0 Unit(s)

2. Required Tools & Accessories Package

GOT IT	TOOL NAME	APPLICATION PURPOSE
☐	Hacksaw or Junior Hacksaw	Required for making clean, straight cuts through the existing PVC downpipe
☐	Spade Drill Bit or Holesaw (25mm or 32mm thickness profile)	For cleanly boring hose entry ports into the plastic water butt body
☐	Combi Drill / Impact Driver	To assemble brackets, mount downpipes, and lock up fixtures
☐	Spirit Level (600mm size) & Tape Measure	Critical to ensure gravity-fed diverter and water butt inlet align perfectly

3. Mandatory Safety Gear (PPE)

GOT IT	SAFETY ITEM	PROTECTION STANDARD
☐	Heavy-Duty Tear-Resistant Work Gloves	Protects hands from sharp PVC plastic shards and saw blades
☐	Impact-Shielding Safety Glasses	Guards eyes from flying plastic chips when sawing or drilling

Present this custom calculated summary list to the building merchant counter assistant to build your project basket easily.

How to Install a Rainwater Collection Water Butt

The DIY Checklist: What You’ll Need

1.

2.

3.

Step-by-Step DIY Installation Guide

STEP

01

STEP

02

STEP

03

STEP

04

STEP

05

STEP

06

Water Butt Installation Calculator

Estimated Materials Required

DIY Project Shopping Checklist

1. Dynamic Calculated Materials & Core Basket Items

2. Required Tools & Accessories Package

3. Mandatory Safety Gear (PPE)

Get the Weekly Top Tip

The DIY Checklist:
What You’ll Need