The City of Ottawa is considering changes to the way it bills for water, adding a base fee in addition to charging for what residents use.

The base charge would amount to about 25 per cent of the cost of the average water bill, according to the proposal.

Dixon Weir, the city's manager of drinking water services, said residents who conserve water would see their bills rise about $5, from about $28 a month to $33 a month.

Moderate consumers and high consumers would actually see their bills drop under the proposal.

How that billing plan fits with the city's water conservation efforts was debated at a briefing for city councillors on Thursday and is likely to be picked up again next week when a city committee looks at the plan.

The proposed change in billing wouldn't add to the city's revenue from water and sewer services, said Weir. But it would make revenue generated from water services more consistent and less dependant on fluctuations linked to weather and usage.

The city is considering the plan because while costs for maintaining water services tend to be fixed regardless of water volume, revenue can vary widely depending on the season.

The city distributes on average 292 million litres of drinking water every day, while the sewer system has more than 5,000 kilometres of sanitary and storm sewers.

The systems have doubled in size since 1987 and have an estimated replacement value of $17 billion, the city said in a statement released Wednesday.