Confirm servicing before the building permit
Hamilton’s additional dwelling unit guidance says servicing must be adequate for the increased development and that City review is required before a building permit. Added plumbing fixtures may mean the existing water pipe or meter is too small. The City identifies a water pipe sizing and hydraulic-load form as part of the review path.
Gather the current service and meter information, the proposed unit’s fixture and plumbing plans, and any prior service drawings. Ask the City which form, calculations, inspections, or upgrades apply to the actual address and configuration. The hydraulic review is a way to test the design against the applicable requirements; it is not a statement that a particular existing pipe has enough capacity.
Keep servicing and land-use decisions distinct
An ADU’s zoning status does not decide water capacity, and a service that reaches the building does not show that it can support additional demand. The City’s pre-permit servicing review, water-provider requirements, plumbing-code review, and any sewer or drainage conditions may involve different evidence and decision makers. Record each response separately, including required upgrades, connection conditions, and unresolved questions.
Use the City’s current form and requirements rather than an old drawing or a result from another property. A qualified designer or contractor may need to provide project calculations, but the final applicable requirements must be confirmed with the responsible City and utility reviewers. For a general checklist of provider, connection, and drainage questions, see ADU water, sewer, stormwater, and drainage checks. Hamilton’s parking rule is a separate question; see Hamilton ADU parking requirements.