Rainwater Harvesting Systems – Maintenance & Safety Info

Even though rainwater collection for household potable water use is common on the Gulf Islands, other BC coastal communities, and the San Juan Islands, so far BC regional health authorities have not established any guidelines for the management of residential rainwater harvesting. Instead, “we” have learned from other jurisdictions where field research and health guidelines exist. In particular, Australia, Texas, Oregon and several Caribbean nations are leaders. Various sources from these regions as well as field knowledge gathered from hundreds of homeowners collecting rainwater on Gabriola, have given us some essential recommendations on maintaining your rainwater harvesting system.

Here are best practices:


  • Monthly: spend about 10 minutes and do a walkabout of your system. Ensure gutters and downspouts aren’t plugged, screens are in place, pipe is not broken or leaking. Check cistern water level with a pole, gauge or tape and record in a log book. Check whole-house filters, change if needed. See that pump pressure is stable and not cycling (if it is, there may be a leak or faulty check valve). Ensure UV is on and not in alarm.
  • Ensure gutters are in good condition and clean; put a screen/strainer over the gutter downspout hole to keep out mosquitoes and other insects from your pipes.
  • Ensure collection cistern has leaf screen in place, hatches are closed and overflow pipe, vents are screened to keep out critters.
  • Periodically – (e.g.) yearly, biennially or at a time you think is necessary, clean your cistern(s) and flush out your collection pipes.
  • Though Century Cisterns are HDPE-UV-stabilized, it’s a good idea to try and screen your cisterns to help reduce sunlight intensity and moderate the water temperature.
  • (We advise) you have a first-rain diverter/bypass with cleanout “knife-style” valve. Ensure it is emptied and ready to go for the next rain after an extended dry-period.
  • Occasionally, add plain 5.25% household chlorine bleach to your cisterns (dose: approx ¾ – 1 cup per every 1,200 gallons of stored water) to help kill organisms that may be present. Hydrogen peroxide — 35% food grade — can be used instead (dose: approx. ¼ to ½ litre per every 1,200 gallons of stored water). Use hose or bucket to move around/ circulate water.

+ Spring/Summer:

  • During extended dry periods (e.g. greater than 7-10 days) ensure your system is ready to bypass/divert the first rain so it cleans your roof and the atmosphere of pollutants. The researched guideline on this is to allow for at least 10 gallons of rain to be diverted for every 1,000 sq ft of collection surface for a “typical roof”. If you have a piped-in first flush diverter, ensure it is empty and ready to accept the first-flush of rain. Otherwise, bypass your cistern and give a solid rainstorm about 2-4 hours of cleaning time before collecting.
  • You should clean and flush your gutters, collection pipes and roof after pollen season.

+ Fall/Winter

  • Continue diverting first rain after any extended dry period.
  • Ensure system is ready to go for the big winter rains. Collect rain continuously.
  • Ensure “wet collection” & supply pipes are protected from freezing by earth or insulation. If you have a “wet-pipe” collection system and extended sub-zero temperatures are forecasted, open up your clean-out/rain diverter and empty the collection pipe of water so it doesn’t freeze and crack your collection pipes!