When you're sleeping rough the act of having a regular hot shower can be a luxury.

Dennis McGuire knows that feeling.

After being evicted from a garage he sublet, he found himself living inside a cold, small campervan parked on a friend's property.

Living without power and washing facilities for four months, he came to rely on a free mobile shower bus service that visited a nearby suburb twice a week.

"It gave you a feeling that you could change ... It was very important," Mr McGuire said.

Unfortunately the mobile shower he once used is unavailable due to major mechanical issues that have seen it taken off the road indefinitely.

The mobile shower bus has been out of action since a major mechanical breakdown. ( Supplied: OneVoice )

Repair bill runs into the thousands

Driver Tim Warne has been operating the bus for two years, visiting the western Sydney suburbs of Liverpool, Parramatta, Penrith and the Hawkesbury region.

The damaged engine is likely to cost tens of thousands of dollars to replace. ( Supplied: OneVoice )

He said the service provided around 200 free showers a month and brought immeasurable benefits to the people who used it.

"It was just the dignity that they would get back and the feeling of community and not being judged," Mr Warne said.

The mobile shower bus is run by charity organisation OneVoice, which has similar purpose vehicles in other capital cities.

The organisation's founder Josh Wilkins said it provided a much-needed facility for people who would otherwise resort to using public toilet hand basins or outdoor water taps to wash themselves.

"They don't have anywhere else to shower, especially in the areas we visit," he said.

While initial costs to replace the engine and fix the fuel system were estimated to be around $12,000, the final figure rose to $32,000 when Mr Wilkins received a quote on Thursday.

A crowdfunding campaign has been set up appealing to the public to assist with the repair costs.

The company SC Johnson, a household cleaning supply company and one of the original sponsors of the bus, has already donated $10,000 to the cause.

'A miniature tent city'

The bus breakdown highlights the broader homeless situation in the city's outer districts.

Hawkesbury's Helping Hands charity operator Linda Strickland said there had been an increase in the number of homeless people in the years she had been working there.

However she said it was difficult to get a true indication of the number across the vast area.

Temporary accommodation tents set up in bushland near the western Sydney suburb of Windsor. ( Supplied: Hawkesbury's Helping Hands )

"In other areas the homeless are more concentrated and more visual," Ms Strickland said.

"Out in the Hawkesbury we have a lot of rural areas where people can camp on the riverbank and we also have a lot of people living in their vehicles."

She described what she called a "miniature tent city" slowing building up in bushland about 1.5km from the centre of Windsor.

"At any given time we could have 30 to 35 people out there.

"We've got families living over there, retired people over there; all ages, all professions."

Many of the residents have been provided with camping equipment that Ms Strickland salvaged from a music festival earlier in the year.

While her organisation solely relied on donations from the public, she said more needed to be done by officials to address a lack of affordable housing.

"The Government needs to make more housing options and lower rents available to get people off the streets."

Engagement brings support

Through the mobile shower bus, Mr Warne is able to engage with those doing it tough and connect them to other support services.

He was able to help find permanent accommodation for a fortunate few including Mr McGuire who now lives in a granny flat with his pet dog.

While Mr McGuire said he did not have much money left over after paying his rent, he felt grateful to have a safe place to sleep each night.

"There [are] people out there who are a lot worse off than me, there really [are]."