Rain Water Harvesting

Rainwater harvesting comes in two forms; basic or complex.

A typical basic system is the common garden butt, fed from a gutter / drainpipe and stored for use in the garden – possibly distributed with the help of a small pump.

The more complex techniques involve draining rainwater from a surface (typically a roof) and feeding it into a sunken tank.

The water is then pumped into your home for uses such as flushing toilets, feeding washing / dishwashing machines, car washing, garden irrigation and so on.

Drinking Harvested Rain Water

Drinking harvested rainwater is not approved of in the UK.

This is mainly because bacteria is almost guaranteed to be in harvested rainwater.

A simple image of birds sitting on your roof should help explain this...

While it is certainly possible to fully filter this rainwater using Ultra Violet systems, the fear is that whereas UV filtration is used happily on “non mains” supplied water from boreholes or well water, these sources tend to be fairly clean to start with.

The Ultra Violet fitration of this water is used as an extra precaution - “just in case” any bugs are in the usually clean water.

However rainwater that’s come off a roof is practically guaranteed to have bugs.

The fear is that the Ultra Violet filter systems won’t be maintained properly and, to be blunt, that people will die.

 

What you can do about it

To counter this you simply need to make sure that you have

a) a good quality Ultra violet system - make sure it is a top quality brand sold by a known and reputable business (hint hint) and not some cheap import from Eastern Europe or the Far East with false claims about foolproof alarms etc.

b) That you change the bulb every year on time

c) That you change the pre-filters regularly.

All of this is easily done. it just needs to actually be done - or you'll probably regret it.

Other Issues with Drinking Rain Water

If that hasn’t put you off then, as we said, filtering rain water certainly is possible.

However you will be stymied by having to have a totally separate water system to your mains water supply.

This is because strict building regulations mean you cannot have a “bi-valve” type of arrangement - whereby you can opt between using mains supplied water vs your own harvested rain water.

(This is mainly due to concerns that polluted water might wash back into the mains water supply).

So you would need to build a separate plumbing system inside your home into which you pump your harvested rain water in from the tank.

This is often impractical and certainly expensive.

Better news: Rain water harvesting for non-drinking uses

However harvesting rain for non drinking uses is a different matter.

This is becoming an increasingly popular way to supply the aforementioned loos, washing machines and so on.

Benefits of non-drinking rainwater harvesting

There is a perhaps surprising extra benefit that concerns planning permission.

It is said that adding a rain water harvester to your plans for a building extension or a new build will dramatically increase your chances of success with your local planning department.

The reasons for this are a mixture of environmental / conservation AND - a crucial keyword - “attenuation”.

Attenuation is the storage and slow release of water.

Attenuating water has benefit such as preventing flood water from rushing into drains (which can cause damage to the mains water system).

It also minimises the risk of feast / famine that comes from reliance,in some areas, on rainwater for public supplies.

 

Will it save you money?

The economic benefits of rain water harvesting are long term.

It’s useful to compare them to solar power systems: your initial outlay will only be repaid over many years.

But meanwhile you will be less likely to run out of water for your garden etc in the event of droughts.

Plus you’ll be helping the environment.