There's a golden rule in politics when it comes to raising taxes.
Increasing the cost of something that people pay for already is difficult enough, but charging for a service they've become used to getting for free is a mug's game.
By introducing a new water charge, John Gormley is breaking that rule -- and unless he goes about it with extreme caution, the early trickles of protest could quickly develop into a raging flood.
While the precise details have yet to be unveiled, it's already clear that every household budget in the country is about to become even tighter.
The Government's initial plan is to install meters in all homes, which it will kindly do for an introductory fee of €175.
The annual cost after that is anybody's guess, but it is unlikely to be much less than €400 per year and will have to be far higher if the Minister is to reach his target of raising €1bn.
The logic behind charging people for water is obvious. Almost every other European country does it, on the grounds that you can't expect people to conserve a precious resource if there's no incentive to do so.
There's little doubt that the amount of water wasted has increased since charges for domestic homes were scrapped here in 1997, a decision that Gormley denounces as "nonsensical and pretty spineless".
On the other hand, few of those countries have the same kind of dysfunctional relationship with H2O that we do.
The recent water shortages, which even affected the richest parts of Dublin in Killiney and Dalkey, came just a few weeks after record levels of rainfall led to flooding across the land.
The quality of our drinking water is often so bad that major cities such as Galway and Cork have had to go for long periods using bottled stuff instead.
Thanks to our antiquated, Victorian-era piping system, an incredible 43pc of drinkable water is lost before it ever reaches our taps.
Most of the new meters will be placed on the public path where the pipe leaves the mains and enters private property, running under gardens, driveways and other houses.
Due to the large number of leaks, what that means in practice is that we'll be paying for water we don't even use.
The recent EU Water Framework Directive reported that half of our rivers and lakes need serious remedial work to satisfy EU standards, raising the prospect of hefty fines from the same people in Brussels who want to impose charges in the first place.
Many people are being asked to conserve water they simply don't have, which sounds suspiciously like the politics of the parish pump.That's why Gormley is fooling himself if he expects the new charge to be greeted calmly by eco-conscious voters who see paying it as nothing more than their patriotic duty.
The reality is that it will be seen as yet another stealth tax on an increasingly cash-strapped public, along with waste collection charges, higher annual motor taxes and carbon levies.
Moreover, people are likely to become even more dissatisfied with the quality of a service that they're suddenly expected to pay for -- and that anger will be taken out on the politicians responsible.
There's also a strong likelihood that a small percentage of households will simply refuse to pay up, which leaves local authorities with an awkward dilemma.
If people don't stump up their waste charges, you can simply leave their bins outside their door. If you cut off their water, however, you can probably expect to find yourself hauled before the European Court of Human Rights within days.
John Gormley doesn't seem to realise it yet, but his latest bright idea is about to open the floodgates. Don't be surprised if the Green Party leader quickly finds himself up to his neck in it.