Many older inner-Melbourne homes have galvanised pipes, installed before a 1970s regulation against their use for drinking water.

Plumber Adam Turnbull said as a result many of his inner-city jobs involved corroded piping, which causing low water pressure and murky water.

Mr Turnbull is re-piping a 1960s apartment building in St Kilda East, and said he could hold up the removed pipes to the sun and see light shining through.

"I was surprised some were even still functioning," he said, adding it would cost about $20,000 to retrofit the building with copper pipes.

Such a job requires accessing plumbing from the interior and exterior, extracting sections of plumbing that haven't seen daylight since original brickwork was finished.

"If you were going to buy an older house or apartment you'd be a fool not to look at the plumbing," Mr Turnbull said.

Zoe Denton of Body Corporate Guardians manages the Hotham Street property Mr Turnbull is working on, and said it was one of three plumbing retrofits on buildings she managed.

About 30 per cent of buildings on Body Corporate Guardian's books have the same problem, which Ms Denton said could cause scalding in showers because of a lack of cold water pressure.

Co-ordinating a building re-plumb was "a nightmare" according to Ms Denton, who said most jobs were funded through an owner's levy.

"The plumbing is the most common of retrofit problems in apartment buildings," she said,

"It can be hard to get all the owners on board, but once we talk to them and the tenants, most people are keen to get the water flow fixed," she said.