Seasonaility | Rain Harvesting by Blue Mountain Co


Failing to consider your planned rainwater uses can lead to challenges with your rainwater quality and quantity. 

Rainwater that’s perfectly suitable for some tasks may not be of an appropriate quality for other purposes. And if you don’t know what you’re using your rainwater for, you’re more likely to run out unexpectedly. 

Considering your purpose and volume requirements and applying the relevant system design principles for your system is therefore necessary if you want to ensure your rainwater is fit-for-purpose and available when you need it. 

Common issues

Tile Roof With Dirt Deposits

Roof area

For every 1mm of rainfall on 1 square metre of roof, you can collect 1 litre of rainwater, so you will want to ensure that you have connected as much roof area as is practical to your tank.

Tanks Render Tandem Set Up

Tank size

If you experience seasonal rainfall or your peak rainfall and water use times differ, you’ll want bigger or multiple tanks to capture enough water for drier times.

Sydney Harbour Rain Clouds

Rainfall seasonality

Rain falls more frequently than most people realise.  Even in places with very seasonal rainfall patterns, rain fall event frequency can be surprisingly regular.  Consult your national or local weather services to determine the rainfall frequency for your area.

Corrugated Rainwater Tank In Front Of Dry Foliage

System design

Not having enough rainwater can be caused by a number of factors.  Surprisingly, low rainfall is often not the key culprit.

Instead, miscalculations (not connecting enough roof area, under-specifying your tank size, overestimating your predicted rainfall), changes in requirements (using your rainwater for more activities than originally planned), compromised water quality and system inefficiencies are often the main cause of volume shortages.

Inefficiencies Gutter Full Of Leaves

System inefficiencies

Inefficiencies around your Rain Harvesting system can reduce the volume of water you collect.  These inefficiencies may include partially or fully blocked gutters and downpipes, leaking pipes or “water bounce” at your tank inlets, which occurs when fast flowing water splashes off your tank screen rather than going through into your tank.

Address with these Rain Harvesting steps


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Rain Harvesting Handbook


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