Roof valleys-Rain water harvesting

Why are they important?

Rainwater harvesting (RWH) can be described as the collecting and storage of rainwater instead of letting it flow away. Rainwater is taken from the roof and directed into the reservoir.

Roof valleys-Rain water harvesting
Save it before you need it

In most rainwater harvesting activities, the roof is the primary drainage basin. Roof valleys play an important part in rain water harvesting.

Roof valleys cause water to flow across the surface quicker than it flows across the character in the absence of valleys.

Valleys in the roof are depressions formed if two roofing slopes intersect. They are designed to hold water and move them from the rooftop to the drain.

The principal purpose of roofing valleys is to permit the water to drain efficiently across the surface, making it accessible for later use.

Roof valleys-Rain water harvesting
A roof valley

In general, rainwater accumulates in gutters, is pumped into the drainpipe, and then is stored in a container. Storage containers can be as simple as rain barrels or something more intricate such as water tanks that supply homes with drinking water. The roof can be a fantastic base for this and is mainly the roof made of metal that has the right coating system.

Choosing the best roofing material for rainwater harvesting

The layout, as well as the maintenance for the valley of the roof, should be strong enough to withstand the weight of snow or heavy rain and also provide an easy route for water to flow.

Sheathing for the roof technique is the same if you are using roofing fabric:

1. Asphalt brick installation

2, Cedar wood ceiling

3. Slate roofing

4. Metal roofs like galvalume, aluminum, stainless steel, and copper

Metal roof valleys are frequently the most popular rainwater collection method.

Metal surfaces have much smaller amounts of organic carbon and other bacteria. That is why a rainwater harvesting device with a metal roof produces water with fewer microorganisms that cause disease.

Galvanized roofing metal is suggested for rainwater harvesting because the roofing panels are later coated with zinc that seals the panels and prevents rust, decreasing the iron levels in the water.

Plastic panels (such as greenhouse roofs) have the highest mounting efficiency.

A roof valley is needed to reduce the risk of damage from prolonged exposure to moisture. In addition, it helps fight mold or algae infestations by protecting the valley areas well from them.

The American Rainwater Collection Systems Association (ARCSA) recommends that “lacquered, powder-coated, or enameled, non-toxic Galvalume (zinc + aluminum alloy) baked or enameled roofs are suitable for potable use with non-toxic finishes. Proper components, tanks, and tank post-treatment”.

What is the minimum roof slope to accommodate rainwater drainage?

The angle of the valley or slope of your roof will determine how quickly and quickly the water will leave your catchment area and the faster the rainwater collection will be.

Water will flow from the roof surface even with a 1-degree angle. But for efficient water flow, the pitch should be 15 to 30 degrees. At this slope, the water will not leak through the roof penetrations.

The angle of the rain is optional. The only thing that matters is the amount of rain in a given area.

Incompatible roof surfaces for rain harvesting

Listing all roofing materials incompatible with rainwater harvesting can take time and effort.

Roofs made of materials harmful to human health – such as asbestos or lead – are incompatible with rainfed harvesting.

Some clay and cement tiles can also cause rain-harvesting problems as they can leach from minerals, oxides, and unsafe coatings.

A roof wash system is advisable, mainly if the water is for human consumption. A roof washer is a device that removes the first 10-15 minutes or more of precipitation from a storage basin. In addition, it will remove dust particles and contaminants that can contaminate the water.    We can collect a maximum of 15.5 cubic millimeters of rainwater from the rooftops of residential homes by collecting all surface precipitation from all the roof surfaces. It equaled 5.6% of the total domestic water supply in 2005.

Valley gutters for proper rainwater drainage

A valley gutter is an area where two main terraces meet or where there is a change in the direction of the terrace.

 Many materials are used in valley gutters, including concrete, lead, and tile. The best rainwater gutters are coated with aluminum or vinyl.

They capture rainwater and direct it away from the foundation.

Because the valley’s gutters are sandwiched between two sloping areas, they are prone to flooding.

Gutters are the primary source of management of water. They direct the water’s flow from the roof’s surface via water spouts to storage areas, most likely in tanks.

Role of Penetrations Sealed in roof valley

The roof is the principal defense of the home and should be as healthy as the structure. Its construction and design should be such that it can shed that water effectively under severe weather conditions.

Valleys and penetrations are among the areas most vulnerable to water intrusion.

Even the most minor roof leak can lead to significant amounts of water damage over time. Proper sealing is necessary to stop water leakage from valleys.

Most roofing membranes are composed of a tough, flexible bituminous substance saturated with petroleum-based solutions like tar, which renders the material waterproof.

Some roofing films come with self-sticking adhesive sanction. These membranes are called self-sealing.

When installed correctly in valleys and all over the penetrations, roof leaks reduce the likelihood of this happening.

In addition, these products provide long-term protection against the ingress of water. In either case, the correct installation method is at the root of the problem.

Managing heavy water flow from roof valleys-Roof gutters

Roof valleys are almost always ignored until the season’s first heavy rains. Then, new householders know that dense rainwater accumulated in one area at a time causes the inside corners of a gutter to flood.

Roof valleys-Rain water harvesting
Protect home from water damage with gutters

Valleys that collect large amounts of rainwater can make gutters useful if equipped with water baffles. Roof gutters can create such runoff that they could slide over channels and later create a hole in the plot of land. The water deflectors are a barrier that catches rainwater and switches it into the drainage system.


Rainwater harvesting improves the water supply throughout the year. In addition, roof valleys provide accessible water flow downward. With this, proper sealing and correct usage of materials in the roof are necessary.

Author: Mahvish ShamimHi, I am Mahvish Shamim. A chemist, and content writer. I love working with WordPress and doing it the right way. Also passionate about spreading awareness about the environmental crisis. Through my skills, I will deliver high-quality work.

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