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Government plans to limit the water pressure in showers have been met with resentment from homeowners.

From February, the Department of Building and Housing is changing the allowable flow rates for showers in new homes exceeding 150sq m to six litres a minute, which plumbers say is little more than a dribble.

There are no controls on shower flow rates and households are free to install shower heads with flows ranging from 5 litres a minute to 24 litres a minute. Some are as high as 35 litres but the average is 13 litres.

New rules also require modifications to hot water cylinders to make them heat pump or solar ready.

This could mean people building homes may have to wait months to install bathrooms as compliant hot water cylinders may not be available because manufacturers have been given only three months to make the changes. The modifications are expected to raise the price of cylinders by about $500.

Steve Bullock, from the country's largest manufacturer of electric water heating cylinders, Rheem, said the changes would require significant re-tooling and redesign.

"We won't make the changes until the rule is firmed up, which they say is going to be the end of October. Then we've only got until February next year to do it. That's an impossible task. Most countries around the world give at least one to three years for manufacturers to gear up for any significant change."

He said people not wanting to wait to build their bathrooms may install non-compliant cylinders or they may be forced to use a more expensive type of heating system.

More than 75 per cent of new homes exceed 150sq m and 75 per cent of New Zealand homes heat water with electric storage cylinders, Mr Bullock said.

Up to 15,000 homeowners per year will have to pay the additional costs for electric water heating.

The new regulations apply to any new building consent issued from February 1 and will cover new homes and renovations. Repair of an existing hot water system will be allowed. It will also be illegal to change any shower head to increase flow rates from February.

Homeowners took their frustrations online yesterday.

"Does this Government have a mandate to mess around with our lives to this degree?" one blogger wrote. "We can't smack our kids, now we can't bathe them as we see fit either?"

One said she "just went and had a really long shower - just to spite them. Bliss. Pressure was fantastic. All four jets powering out as much as they could. Beautiful".

And another wrote: "Isn't it extraordinary. The world finance markets are in total disarray, NZ is staring down the barrel of much higher inflation, large Govt deficits, massive over-expenditure of Govt departments, much higher unemployment, massive increases in people living in hardship and yet all these dickheads can do is regulate how much water comes out of the shower."

National's building and construction spokesman Nick Smith said the new rules are an example of the "nanny state gone mad".

He said less water in the shower is not as comfortable, not as good for cleaning, and not something a government should be interfering in.

But Building and Construction Minister Shane Jones said the standard "provides for hot water energy savings of 20 per cent over current averages using modern technology to save the homeowner money and reduce the possibility of blackouts and electricity shortages".