Standing knee deep in a cement tank of milky water, Dinesh Kumar dunks clothes before vigorously scrubbing them with a brush at an outdoor laundry in the Indian capital.

After quitting high school, Kumar joined his father among the ranks of traditional washermen who have hand-cleaned the sprawling city's dirty clothes for generations.

Over the years, the work of "dhobi wallahs" has modernised to a degree, with industrial machines now used at some laundries for washing heavier loads of curtains, bed covers and towels.

But 32-year-old Kumar said most of the washing was still done by hand. The more delicate and expensive garments also needed to be handled carefully to ensure sewn-on beads or embroidery were not damaged.

"I start work at the crack of dawn and wash about 100 clothes by evening," Kumar told AFP as washermen nearby swung damp trousers over their heads before thrashing them against concrete stone slabs.

After every wash in a milky bath of bleach and detergent, Kumar inspects the clothes closely to ensure they are spotlessly clean.

"Most of the clothes come here from hotels, embassies or beauty parlours. If we don't wash properly, they will stop sending the clothes over."

Once the clothes are scrubbed, Kumar rinses them in the cement tub, wearing a plastic sheet around his waist to stop his rolled-up trousers getting wet.

Such so-called "dhobi ghats" are normally set up next to a river, but these washermen in New Delhi rely on well water stored in cement tanks and pools for their supply.

After the clothes are hung out on lines strung up on terrace rooftops to dry, they are ironed, often by the women in the washermens' family.

But Ram Lal Kanojia, who runs another small laundry nearby, said younger generations were not keen on joining the family business, as India's economy grows rapidly.

"My children are studying computers and management. They don't want to wash clothes all their life like me," said Kanojia, who earns about 25,000 rupees ($374) a month.

"It's too much hard work and not much money."