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The short rains are approaching, making now the time to prepare your roof, gutters and water storage system.

A properly set-up roof can do more than keep your home dry. It can help collect thousands of liters of water for cleaning, laundry, gardening, livestock and other everyday needs.

Effective rainwater harvesting is not just about buying a water tank. Your roof, gutters, downpipes and tank must work together efficiently. MRM’s Raingain Systems combine gutters, downpipes and water tanks to help homeowners collect and store rainwater.

Why Prepare for the Short Rains Now?

Kenya’s October- December period is commonly known as the short rains season, although rainfall varies considerably across different parts of the country.

Current climate outlooks indicate a possible El Niño influence toward the end of 2026, which could enhance rainfall in some parts of Kenya. Forecasts can change, so homeowners should keep checking updates from the Kenya Meteorological Department.

Water Services Regulatory Board (WASREB)’s latest sector performance report highlights continuing water-access challenges in Kenya, making rainwater harvesting a useful supplementary source for households particularly where mains supply is intermittent.

How Much Rainwater Can Your Roof Harvest?

Before choosing a water tank, start with your roof. The basic calculation is simple:

Harvestable water (litres) = Roof area (m²) × Rainfall (mm) × Runoff coefficient

One millimetre of rainfall falling on one square metre of roof produces approximately one litre of water before accounting for losses. The runoff coefficient accounts for water lost through evaporation, splashing and other factors.

For example, a 150m² roof receiving 150mm of rainfall: 150 × 150 × 0.8 = 18,000 litres

A smaller 90m² roof receiving 80mm of rainfall: 90 × 80 × 0.8 = 5,760 litres is enough to fill a 5,000-litre tank, provided your gutters and downpipes can capture and transfer the water efficiently.

Tank capacity and gutter capacity need to be considered together. There is little benefit in installing a large tank if your roof and gutter system cannot move enough water into it.

Choosing the Right Water Tank Size

The right tank depends on your household size, daily water consumption, available roof area and how much water you want to store between rainfall events.

As a general planning guide:

For supplementary use, a smaller tank may be sufficient. Larger households or those with higher water demand may benefit from 5,000 L or 10,000 L storage.

What Is the Price of a 5000 Litre Water Tank in Kenya?

If you’re researching the price of a 5,000-litre water tank in Kenya, MRM’s Raingain Water Tanks currently list the 5,000L round PVC tank at approximately KES 55,416.68. The 3,000 L model is around KES 29,540.56, and the 1,500 L model is around KES 19,185.24.

What Is the Price of the 10000 Ltr Water Tank?

The Rain Gain 10,000 L round PVC tank is currently listed at approximately KES 109,899.56. Prices may change, so check the current listing before purchasing.

Explore MRM Rain Gain Water Tanks.

Don’t Forget Your Gutters

Your water tank can only store the water that reaches it, making gutters essential to rainwater harvesting. A 150mm half-round gutter with a 100mm downpipe is a practical starting point for many homes, though the right size depends on roof area, design, rainfall intensity and outlet placement.

Larger or complex roofs may need additional downpipes to prevent overflow.

MRM’s Raingain Systems include 150mm half-round gutters (approximately KES 1,740 per piece) and 100mm downpipes (approximately KES 1,450 per piece).

Explore Raingain Systems.

Your Pre-Rains Roof and Gutter Check

Before the short rains begin, take some time to inspect the entire route that water will take from your roof to your tank.

1. Clear Your Gutters

Remove leaves, dust and debris. Blocked gutters cause overflow onto walls, fascia boards and foundations instead of your tank.

2. Check Your Ridges & Valleys

Look for gaps, loose sections or corrosion at roof junctions, which can become leak points when damaged.

Explore Ridges & Valleys.

3. Inspect your Flashings

These seal vulnerable areas where the roof meets walls and gables. Address any loose or damaged flashings before the rains arrive.

Explore Flashings

4. Check the gutter fall

Water should flow naturally toward the downpipe. A level or incorrectly angled gutter can hold standing water or overflow.

5. Inspect your downpipes

Make sure they’re securely connected, free of blockages, and discharge cleanly into the tank without leaking.

6. Check your tank and overflow

The tank should sit on a stable, level base, with the overflow pipe directing excess water away from the foundation.

7. Check your roof sheets and fixings

Look for loose sheets, damaged fasteners, gaps or corrosion. A small problem can quickly become a larger leak when heavy rain and wind arrive.

How a Rain Water Harvesting System Works

Think of rainwater harvesting as a complete chain rather than a single product:

Roof → Gutters → Downpipes → Water Tank → Storage → Use

Your roof collects the rainfall, gutters capture the runoff, downpipes carry it down from the roofline, and the tank stores it for later use. Supporting accessories matter too.

Ridges & Valleys help manage vulnerable roof junctions, while Flashings protect areas where the roof meets walls and other structures. When these components work together, your roof becomes part of your home’s water management system.

Get Your Roof Ready Before the Rain Arrives

The best time to discover a blocked gutter or leaking roof is before the rain starts. Inspect your roof, gutters and water tank now, and make sure the roof area, gutter capacity and tank size all work together.

With the short rains approaching, preparing your rainwater harvesting system now can help you capture more of the water that falls on your roof.

This article is for general information only. Rainwater harvesting yields, gutter requirements, tank sizing and product prices vary depending on your roof, location, household needs and system design. For a system suited to your specific requirements, consult a qualified installer or MRM representative.