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Is bigger better?

Posted by Barry Nutley on 11 February 2009 at 9:38 am

Renewable energy can be a little confusing. For example, explaining to some people that doubling the size of a solar thermal system isn't necessarily a good thing, but doubling the size of a solar PV system is; doubling the size of a heat pump isn't a good idea, but doubling the size of a wind turbine is. That's why it's a good idea to employ a consultant to help you solve these mysteries. But then I would say that!

So what's that got to do with rainwater harvesting? Well, typically most of us rainwater harvesting experts suggest that it is not a good idea to install a bigger tank than is necessary. I am, however, leaning towards the idea that going bigger, is a good idea (normally a sales tactic employed by some sellers, of which I am not...).

It is relatively simple to work out the size of tank you require (annual rainfall, roof space and type are the main ones), and there are many calculators that are free to use on the web. Some are more complicated than others, asking information regarding garden size, how many times you clean your car and how many weeks drought protection you need? The one at Rainwater Storage is easy, takes seconds to use, and only asks the key questions.

Fundamentally all the calculators use the same rainfall data from the Met Office, from 1971-2000. And to me, that seems such a long time ago. We know that our average rainfall has risen since the previous measurement in the '60's. So does this mean that it is likely to rise even more? Possibly? Probably?

I know what you are all thinking - if rainfall is increasing, then what are we worried about? Unfortunately, we are using more water (remember the beer fact in the last blog? and look at one of the new facts at the end of this one), and our reservoirs haven't been improved accordingly. So we still need to be mindful of our water usage, and/or save more.

The human race, although being extremely clever(?), doesn't seem as good as some of our animal friends at saving for a rainy day. Take for example squirrels. They store nuts for the winter. Polar bears feed up before hibernation (I know they don't technically hibernate, but..) and so on... So why don't we store more when we can?

Recent snow, and heavy downpours have provided us with plenty of water. 200mm of rain has fallen, already, this year in the south east. On a standard roof of 40m2, you could have collected over 5,000 litres of water. That's enough for over 500 flushes of your loo! Unfortunately, much of this water has found it's way into the sea. Imagine we were all able to collect this: would flooding in parts of the south east be so bad?

As we know, scientists predict that these freak weather conditions, caused by climate change, are likely to increase. So perhaps we should be far better prepared to take advantage of rain, for example, when it comes. In order to save it for other freak conditions, such as those being experienced in parts of Australia?

So, to answer the question "is bigger better?". I think so, and would advise you to dig a bigger hole, put in a bigger tank for a few hundred pounds more, save more water, save more money, reduce the risk of flooding, and have a better looking garden than your neighbours when we have a drought.

If you would like answers to a specific query, then please ask it here, or visit our website, where you will find a contact us page.

And finally, a couple of facts to bear in mind:

  1. Two hundred scientists in 50 countries have identified water shortage as one of the two most worrying problems for the new millennium (the other was climate change).
  2. On current trends, over the next 20 years humans will use 40 per cent more water than they do now.

Happy harvesting...

Photo by Javier Volcán

About the author: Barry Nutley is co-founder and director of Viridis Energie Consultants

If you have a question about anything in the above blog, please ask it in the comments section below.

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