For the sixth time in seven years, Phoenix leaders will vote on raising water and sewer rates — but this time is different because it includes conservation measures.

Phoenix provides a monthly water allowance to all 430,000 customers. But if the City Council approves during its Wednesday meeting, the allowance will go down. And about 90% of customers will pay for additional water at least once — if they continue to use the same amount. Depending on the season, the price per unit would be roughly $4. One unit equals 748 gallons.

The unit increase would be in addition to requested rate hikes. They include a 26% increase for water over two years and 20% for wastewater.

Last year, Phoenix declared a Stage 1 Water Alert due to a Colorado River shortage. The Water Services Department said the cost of raw water has increased 35% this fiscal year, personnel is up 38% and water chemicals are up 136%. The department said wastewater chemicals are 51% higher and personnel costs are up 16%.

The department has held many public meetings to explain the proposal and has a water and wastewater estimator for single-family homes to compare current and proposed rates.

Because each customer — whether a single-family residence, business, nonprofit or government entity — is unique, it can be tricky to apply general numbers to everyone. If customers take no conservation steps and the proposed allowance is approved, here’s what the city estimates:

• 9% of all customers will remain unaffected and pay for no additional units.
• 4%-5% of customers who have traditionally been below the allowance will exceed for the first time.
• 43% will sometimes be over the allowance and pay per additional unit.
• 44% of customers will be over the allowance and pay per additional unit

The estimates above are based on no reductions in water use under the proposed allowance. 

 Separate from the monthly water allowance changes is the following water and wastewater rate proposals: