The students of Building Services Engineering at Waterford Institute of Technology began the new term with a visit to Longford Cathedral, which is under reconstruction after a devastating fire in 2009.

But while most visitors admire the exterior, some of the most impressive aspects of the job are out of sight — like the rainwater harvesting system that will use the water freely supplied by the heavens to flush toilets and supply other areas where treated water is unnecessary.

“The big issue with water supply in our buildings — commercial and domestic — is that the water has been chemically treated to make sure it’s fit for human consumption, but yet we waste it by using it in the toilet or on the garden or washing the car,” says course leader Tom O’Brien.

“With a rainwater harvesting system, the rainwater is collected and diverted through a filtration system and then up to a pump that feeds it into the toilets. In the average house, about a third of waster use is in toilets, so it makes sense.”

And it’s not just to the clouds we should be looking — our sinks, showers, and baths are another ready source of reusable water.

“We don’t use this ‘grey water’ very much here. In the UK they would use it more and a typical application would be again flushing toilets, washing cars, watering the garden. It needs filtering but it’sessentially clean water, and so long as it doesn’t go into the drinking water, it’s OK to reuse.

“This kind of system isn’t particularly new and it’s not rocket science, but if you don’t need it by regulation or by being affected in your pocket, most people don’t do it. The result is it’s a little bit expensive but the more there’s a demand for it, the more price will come down.”

Such systems best suit new builds, and although it’s possible to retrofit an existing house, the reality is most householders will be looking to more modest modifications to help them save on their water bills.

First, says Tom, get to know your loo. If your toilets were installed after 2001, it’s likely you have a conservation-conscious six litre cistern, although even that could be made more efficient by converting it to a dual flush system allowing a choice between a full flush and a three-four litre flush, enough to wash away number ones and probably many number twos too.

Older toilets can have anything from nine to 14 litre cisterns, which are far bigger than what’s needed but you can buy a cistern displacement device — basically a sealed plastic or polythene pouch or box of two-three litres capacity that sits inside the cistern, reducing how much water it can hold and how much the toilet uses with each flush.

“You can do a DIY thing by filling a two-litre bottle and putting it in the cistern,” says Tom. “You can put a brick in too but they should really be covered in a plastic bag because a brick will shed little bits of material over time that will clog the toilet.”

There are other DIY devices that can be helpful, but Tom says the biggest modification that has to take place is in the public mindset.

“We need a bit of consciousness of the amount of water we’re using. We’ve got into bad habits over the years. Simple things like putting the plug in when you’re washing your hands, or using a basin for washing vegetables rather than just leaving the water running — we don’t do that any more.

“Even washing teeth — years ago you would always just have a glass of water and wash your teeth from that rather than from a constant flow of water. Some wash hand basins had a built-in holder for your cup or glass — you don’t really see that now.”

Other common crimes against conservation include filling the kettle to full capacity when you only need a mug’s worth, putting on the dishwasher or washing machine when they’re only half full, watering the garden by hose, and using a running hose to wash the car instead of a few buckets of water.

Ignoring leaks is another problem — a leaking cistern or dripping tap can waste thousands of litres of water a year while a serious leak can lose hundreds of thousands.

“A lot of leaks would be in the incoming water under the footpath so it’s below your ground floor level and you wouldn’t notice it at all, particularly in a climate like Ireland where it’s raining a lot and the fact that you come out in the morning and see your footpath is wet wouldn’t be particularly unusual.”

Metering will show up serious leaks, but Tom says it would be useful if the information from the meter outside the house was available in easily readable form inside too.

“We have Owl meters for electricity where you can get a clamp that you put on your incoming electricity supply and a little visual display that you can put inside the house to show your power usage,” he says.

“When you’re going to bed and switching everything off, you should see it going down to 100-150 watts, but if someone has left a TV or computer on, this will be right in your face telling you that you are still using 500-600 watts.

“Something similar that would visually show you your water usage would be very useful in helping people to adjust their habits. Because a lot of it is common sense, but the old common sense isn’t that common anymore.”

Two valuable websites with information about water usage and water conservation tips are greenhome.ie and taptips.ie.

Some water conservation devices include:

Aerators

An aerator is a nifty little device that screws onto to shower heads and taps and can cut water flow by half without making it feel like your torrent of water has turned into a trickle. It works like a sieve that splits the flow of water into many tiny streams, pushing air into the streams so that less water comes out but the pressure remains strong.

Cistern Displacement Devices

Popular ones on the market include the Hippo, the Toilet Tank, and the dubiously named Toilet Tummy.

They sits in the cistern, reducing the water holding capacity of the cistern, cutting the amount it uses each time you flush. For example, a three-litre Hippo bag will turn a nine-litre cistern into one that operates using six litres per flush.

Flush Restrictors

This works by altering the toilet handle to give control over the length of the flush. You push the handle down to start the flush but let it go to finish it as soon as the bowl is clear so if the clearing job only needs seconds, that’s all you give it.

Dual Flush Conversion Kit

More common in public toilets than in domestic settings, the dual flush system gives you two push button flushes, one using the full capacity of the cistern and one about half that amount. Diplomatically speaking, the reduced flush is for number ones and the full one for number twos.

Shower Timer

They don’t come more low-tech than this. It’s essentially a waterproof egg timer with a suction pad that sticks on to your shower door or tiles and uses four minutes worth of sand instead of the standard three minute kitchen version. Four minutes is the target time most water conservation bodies — and defence forces — say is adequate for a shower.

Leak Detector Dye Tablets

These won’t solve a leak but they’ll tell if you have one. The tablet is placed in the cistern and the toilet left unflushed for as long as the manufacturer recommends — usually up to 30 minutes. If any of the dye appears in the toilet bowl, you’ve got a leak, otherwise the dyed water would remain in the cistern and wouldn’t have to be used to top up the bowl. Your next step is to call a plumber. Food colouring can be used in the same way.

Water Butt

A modern, and safer, take on the old-fashioned rain barrel, a water butt is basically a large plastic barrel-shaped container that is attached to the downpipe that leads from your roof gutter so that rain water coming down the pipe into the drain is caught and carried into the butt first. It’s covered for safety and there is a shut off valve that sends excess water on down the pipe and into the drain once the butt is full. A tap at the bottom allows water be drawn off for watering plants, washing cars, and other outdoor uses.