Rainwater harvesting and irrigation planning for a Burnaby custom home

Every summer the same thing happens on the lots we build in Burnaby. The new lawn goes in during June, the reservoirs drop, the region tightens its watering stage, and by August the owner is standing on a brown yard holding a hose they are allowed to use one morning a week.

Rainwater collection is the way around that. The time to plan it is while the excavator is still on site, which is the part most people miss.

What the watering rules actually say

Metro Vancouver's regional watering restrictions are in effect every year from May 1 to October 15, and the City of Burnaby enforces them. At Stage 1, the normal summer setting, a residential lawn gets one morning per week: automatic sprinklers from 5 to 7 am, manual watering from 6 to 9 am. Which morning depends on your address and the stage in effect, so check the regional page before you set a controller. In a dry year the region moves to a higher stage and the lawn allowance shrinks; in 2026 the one-morning-a-week window came back on September 1.

Trees, shrubs and flowers are treated differently. Under Stage 1 and Stage 2 you can water them by sprinkler any day between 5 and 9 am, and at any time by hand-held hose with a shut-off nozzle, soaker hose, watering can or drip irrigation. Vegetable gardens can be watered any time. A newly seeded or sodded lawn can get a City of Burnaby permit that allows watering outside the restricted hours for 21 consecutive days, which is how a spring lawn survives its first month.

Then there is the line that makes this whole post worth writing. The regional rules state that they "do not apply to the use of rainwater, gray water, any forms of recycled water, or other sources of water outside the GVWD/municipal water supply system" (Metro Vancouver). Water you caught off your own roof in March is yours to use in August, on any day, at any hour.

The roof already collects it

Burnaby gets enough rain that the BC Building Code requires a second plane of protection behind the cladding, the rainscreen, in any location with more than 1,000 mm of annual rainfall, and Burnaby is one of those locations. Every square metre of roof on a custom home is already a collection surface. The gutters and downspouts are already moving that water to a storm connection. Harvesting means putting a tank between the downspout and the outlet, then using the water before it leaves the lot.

How much water that is depends on the roof area, the roof material, and how much of the wet season you want to store. We run that number per house from the roof plan, not from a rule of thumb, because a low-slope roof on a Brentwood infill lot and a big hipped roof on a Deer Lake estate lot collect differently.

Rain barrels or a cistern

The City of Burnaby sells rain barrels at its Eco-Centre, one per household, and each holds up to 341 litres. A barrel under a downspout is a fine way to water planters and a vegetable bed. It is not an irrigation supply for a planted lot. A hot week empties it, and it cannot feed a pressurized zone.

A custom home with real landscaping wants a cistern. That usually means a buried polyethylene or concrete tank near the downspouts, with a leaf screen and a first-flush diverter upstream so the first dirty run-off from the roof goes to the storm system instead of the tank. Inside the tank there is a submersible pump on a float switch, and after the pump there is a filter before the water reaches the drip lines. Above ground, the tank shows up as a lid at grade and a small control box.

The reason to decide this at design stage is simple. The tank hole gets dug with the foundation excavation, the overflow gets tied into the storm connection while that trench is open, and the pump power and controller wire share a trench with the exterior lighting. Add the cistern after the landscaping is finished and every one of those trenches gets dug twice.

Irrigation only, and why we keep it that way

The 2024 BC Plumbing Code allows non-potable water systems to serve toilets, urinals, trap seal primers and irrigation systems, and it includes prescriptive provisions for rainwater harvesting systems. The same provincial bulletin says harvested rainwater needs to be treated, and that where a fixture combines potable water with harvested rainwater, the potable side has to be protected by a backflow preventer.

Our position on most custom homes is to stop short of that. Collected rainwater goes to irrigation and nothing else. It runs on its own piping, labelled as non-potable, with no connection to the house plumbing. That keeps the treatment equipment, the extra permitting and the cross-connection design out of the project. If an owner wants rainwater flushing toilets, it can be done under the code, but it becomes a treated water system with its own design, and at that point it belongs in the same conversation as whole-home water filtration.

A cistern is a hole in the ground next to a hole in the ground. Dig them on the same day or pay to dig twice.

Icon Projects Team

Drip lines for the beds, spray for the lawn, and less lawn

Drip irrigation puts water at the root at low pressure with almost nothing lost to evaporation, and under Stage 1 and Stage 2 it can run on any day at any time for trees, shrubs, flowers and vegetables. It also runs happily on the pressure a cistern pump provides. Spray heads throw water into the air across a lawn, lose a share of it to wind and heat, and on municipal water are stuck inside the one-morning window.

So the design follows the rules. Planting beds, hedges and the vegetable garden get drip zones fed from the cistern. Lawn gets spray zones, and we make the lawn smaller than the owner first asked for. The City of Burnaby's own guidance is that a healthy lawn needs only 25 mm of water per week, which is one short cycle, and a tank-fed system can deliver it on whatever morning suits the grass rather than the calendar.

On a Government Road or Buckingham Heights lot with a large garden, this split changes the whole planting plan. A designer who knows the beds are on drip will plant differently than one who assumes a sprinkler will hit everything.

Smart controllers and the two-source problem

A weather-based controller uses a local forecast or an on-site rain sensor to skip cycles after rain and shorten run times in cool weather. It schedules zone by zone, so drip beds and lawn spray can run on separate programs. That much is worth having on every system.

What it cannot do is read the regional stage. It does not know whether Metro Vancouver is at Stage 1 or Stage 3, and it does not know whether your house number is even or odd. Any zone that draws from the municipal supply has to be programmed by a person to the permitted day and hours, and reprogrammed when the stage changes. Cistern-fed zones are free of that, and the cleanest systems we build put a valve between the two sources so the controller draws from the tank first and only opens the municipal line when the tank runs low, on a schedule that respects the restrictions.

The controller wire and the pump circuit go in at electrical rough-in. That is a small detail with a big consequence: a controller added later ends up on the garage wall with a wire stapled across the siding.

Backflow prevention where irrigation meets the house

Any irrigation system connected to the house supply is a cross-connection, because fertilizer, soil and standing water in the zone lines can siphon back into the drinking water if pressure drops. An approved backflow prevention device on the irrigation branch stops that.

In Burnaby this is now its own permit. Since November 1, 2024 the City has issued a separate Backflow Prevention Device Permit instead of handling these devices under the plumbing permit, with testing done under the CSA B64.10 field-testing manual and the Burnaby Plumbing Bylaw and the test reports handled by the City's Cross Connection Control section. The device has to sit where it can be reached and tested, which means we plan its location in the mechanical room or on an exterior wall, never behind a finished cabinet.

A cistern-only system with no municipal tie-in avoids the cross-connection on the irrigation side. It does not avoid the drainage question, which is where the tank interacts with the rest of the site.

Tie it into the site drainage plan

The BC Building Code requires foundation drains to run to a sewer, a drainage ditch or a dry well. Their job is to carry water away from the foundation. A full cistern overflowing during a November storm is a lot of water, and the worst place to send it is into that perimeter drain, where it competes with the water the drain is already trying to remove from around the footings.

So the overflow goes to the storm connection or to another outlet shown on the site drainage plan, and the tank's own location follows the grading. On a sloped Capitol Hill or Sperling-Burnaby Lake lot the tank sits where its overflow runs downhill and away from the house. The downspout diverter that sends roof water into the tank also changes where roof water goes on the drawings, so the site drainage plan submitted with the permit has to show the tank, the diverter and the overflow route, not just the downspouts as they would be without a system.

The same thinking applies outside Burnaby. In Coquitlam, on a Burke Mountain lot with a creek below, the overflow route is a riparian question as well as a drainage one. On a rural Abbotsford property on a well and septic, the cistern does a second job: it takes irrigation load off a well that may already be working hard in August.

Get the tank into the excavation plan, get the overflow onto the drainage drawing, and get the backflow permit filed with the plumbing permit. Do those three things and the irrigation system is a set of zone valves and a controller. Skip them and it is a second construction project in a finished yard.

Frequently asked questions

Can I water my garden with collected rainwater during Metro Vancouver watering restrictions?

Yes. Metro Vancouver's lawn watering regulations state that they do not apply to rainwater, gray water, recycled water, or any water from outside the municipal supply. A cistern filled from your roof can feed irrigation on any day and at any time. The restrictions still apply the moment the system draws from the municipal connection, so a two-source system has to be programmed with that in mind.

When do lawn watering restrictions apply in Burnaby?

Metro Vancouver's regional watering restrictions are in effect every year from May 1 to October 15, and Burnaby enforces them. At Stage 1 a residential lawn can be watered one morning per week, with automatic sprinklers permitted from 5 to 7 am and manual watering from 6 to 9 am. The permitted day depends on your address, and higher stages cut the lawn allowance further, so check metrovancouver.org before you set a controller.

Is drip irrigation allowed during Burnaby watering restrictions?

Drip irrigation on trees, shrubs, flowers and vegetable gardens is allowed on any day at any time under Stage 1 and Stage 2 of the regional plan, along with soaker hoses, watering cans and a hand-held hose with an automatic shut-off nozzle. Lawns are the exception: they are limited to the one-morning-a-week window at Stage 1. That is why we zone drip lines for beds and keep spray heads for lawn only.

How big a rainwater tank does a Burnaby custom home need?

It depends on the roof area feeding the tank, how much garden you are irrigating, and how long a dry stretch you want to bridge. We size it per house from the roof plan and the planting plan rather than picking a standard tank. The City of Burnaby sells rain barrels that hold up to 341 litres each, which is enough for planters, but a planted lot on Government Road or in Buckingham Heights usually calls for a buried cistern many times that size.

Can collected rainwater be used inside the house in BC?

The 2024 BC Plumbing Code allows non-potable water systems to serve toilets, urinals, trap seal primers and irrigation, and it includes prescriptive provisions for rainwater harvesting systems. Harvested rainwater has to be treated for indoor use, and anywhere it meets the potable supply the potable side must be protected by a backflow preventer. On most custom homes we keep collected rainwater on a separate irrigation-only line, which avoids the treatment and cross-connection design entirely.

Does an irrigation system need a backflow preventer in Burnaby?

An irrigation system connected to the house supply is a cross-connection and needs an approved backflow prevention device. Since November 1, 2024 the City of Burnaby issues a separate Backflow Prevention Device Permit for these devices instead of covering them under the plumbing permit, and questions on the test reports go to the City's Cross Connection Control section, with testing done under CSA B64.10 and the Burnaby Plumbing Bylaw. A cistern-only system with no municipal tie-in avoids the cross-connection on the irrigation side, but the tank overflow still has to be handled.

Where should a cistern overflow go on a Burnaby lot?

To the storm connection or another outlet approved on the site drainage plan, never into the foundation perimeter drain. The BC Building Code requires foundation drains to run to a sewer, a drainage ditch or a dry well, and their job is to keep water away from the foundation, so routing a full tank's overflow into them works against the house. On a sloped Capitol Hill or Sperling-Burnaby Lake lot we also place the tank so that overflow runs downhill away from the building.

Can a smart irrigation controller follow Metro Vancouver's watering days automatically?

A weather-based controller can skip cycles after rain and adjust run times, but it does not know which stage the region is at or whether your address is even or odd. Someone still has to program the permitted day and hours for the municipal source and update them when the stage changes. What the controller can do well is run cistern-fed drip zones on their own schedule, since those are not subject to the restrictions at all.