---
title: "Rainwater Harvesting Systems New Construction | AVANORTH"
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description: "Rainwater harvesting systems for new residential construction. System components, sizing, Ontario regulations, and new build installation advantages."
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"og:title": "Rainwater Harvesting Systems New Construction"
"twitter:description": "Rainwater harvesting systems for new residential construction. System components, sizing, Ontario regulations, and new build installation advantages."
"twitter:title": "Rainwater Harvesting Systems New Construction"
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AVANORTH Home
**Green Building**·February 21, 2026· 4 min read
# **Rainwater Harvesting Systems in New Builds**
Collecting and using rainwater reduces municipal water demand, lowers utility bills, and supports sustainable site management. Here is how to integrate rainwater harvesting into new construction.
**AVANORTH Team**
AVANORTH Construction
## Why Harvest Rainwater?
Rainwater harvesting captures precipitation from roof surfaces, stores it, and makes it available for non-potable uses: landscape irrigation, toilet flushing, laundry, vehicle washing, and cooling tower makeup water. In Ontario, the average residential roof captures 80,000 to 120,000 litres of rainwater per year (based on an annual precipitation of approximately 800 mm and a roof area of 100 to 150 square metres). That is a significant volume of clean water that currently flows into storm sewers.
The benefits of harvesting this water include:
- Reduced municipal potable water consumption (outdoor water use accounts for 30 to 50 percent of residential water consumption in summer months)
- Reduced stormwater runoff from the property, which helps manage urban flooding and reduces combined sewer overflows
- Lower water and sewer utility bills
- Reduced strain on municipal water treatment and distribution infrastructure
## System Components
A rainwater harvesting system for a new residential build consists of:
- **Collection area:** The roof surface. Metal and concrete tile roofs are ideal because they shed water cleanly. Asphalt shingle roofs are acceptable for non-potable use but may contribute granules initially. Treated wood or lead-flashed roofs should be avoided.
- **Gutters and downspouts:** Standard residential gutters and downspouts convey water from the roof to the storage tank. Leaf screens at the gutter and a first-flush diverter (a device that discards the first several litres of each rainfall, which contain most of the roof surface contaminants) improve water quality.
- **Storage tank (cistern):** Underground polyethylene, concrete, or fibreglass tanks are the standard for residential installations. Tank sizing depends on water demand, roof area, and local rainfall patterns. For a typical Ontario home using harvested water for irrigation and toilet flushing, a 5,000 to 10,000 litre tank provides adequate capacity.
- **Pump and distribution:** A small pressure pump delivers water from the cistern to the point of use. A pressure tank and pressure switch provide consistent water pressure. The pump should be equipped with a dry-run protection switch.
- **Filtration:** A pre-tank mesh filter removes leaves and debris. A post-tank sediment filter removes fine particles before distribution. For toilet flushing, a 50-micron filter is typically sufficient.
- **Municipal water backup:** An automatic switchover valve or air-gap backup connection supplies municipal water to the system when the cistern is empty. The air gap prevents any possibility of contaminated rainwater backflowing into the municipal water supply.
- **Overflow:** A properly sized overflow pipe directs excess water to the storm sewer or a surface discharge point (rain garden, swale, or dry well).
## New Construction Advantages
Installing a rainwater harvesting system during new construction is significantly easier and less expensive than retrofitting:
- The cistern can be installed during excavation, before backfilling and landscaping. No need to dig up finished yards.
- Plumbing for a dual water system (potable for sinks and showers, non-potable for toilets and outdoor taps) can be roughed in during the framing and plumbing stage at minimal additional cost.
- The pump and filtration equipment can be incorporated into the mechanical room layout.
- Pipe routing from the cistern to the building is cleaner and less expensive when done during initial construction.
## Regulatory Considerations in Ontario
Ontario's Building Code does not explicitly prohibit rainwater harvesting for non-potable indoor use, but it does require:
- Complete separation between the potable water and non-potable water systems (cross-connection prevention)
- Clear labelling of all non-potable water outlets ("CAUTION: Non-potable water. Do not drink.")
- An air gap or reduced pressure backflow preventer between the municipal backup supply and the rainwater system
- Plumbing installations must be performed by licensed plumbers and must comply with the Ontario Plumbing Code
Some municipalities in the GTA offer stormwater management credits or subsidies for properties that implement rainwater harvesting, recognizing its benefit to the municipal storm sewer system.
At AVANORTH, we design rainwater harvesting systems into new builds where client interest and site conditions support it. The systems are practical, well-integrated, and designed to provide years of reliable service while reducing the property's water footprint.
#rainwater #harvesting #sustainable
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