Author: Danny Kapsch – new board member and stormwater guru at Portland’s Bureau of Environmental Services

5 Tips for Effective Rainwater Harvesting in Portland

Portland averages around 37” of rain each year, mostly coming in the late fall, winter and spring. Ever consider catching some of that rain and saving it for later use? Rain barrels can be a great way to harvest some of Portland’s bounty for summer irrigation or use during an emergency situation. In fact, because most of Portland’s drizzle comes during the months when we don’t need it for watering veggies and flower pots, capturing rainwater for use in an emergency situation could be the primary reason for installing a rain barrel in the Pacific Northwest.

Tip 1: Go Big or Go Home


Mother Nature giveth and she taketh. Collect it while Ma’s being generous!

Unfortunately, it’s often difficult to capture enough water to make a dent in irrigation during the dry summer months. It can definitely help in kicking off the growing season, but past that first week or so, you will likely be dragging out the garden hose. If you are considering a rain barrel for irrigation purposes, consider installing more than one 55 gallon barrel. A series of rain barrels or a larger cistern can do the trick–especially given a summer shower or two to recharge the system. In an emergency situation however, even one barrel could make a huge impact by providing a source of water to get you through.

Tip 2: Rock the Overflow


The wrong way to plumb overflow

Given that 1,000 square feet of roof will generate over 22,000 gallons of water in a typical rain year (in Portland), the overflow is the most crucial element of a catchment system. In other words, your barrels or cistern is bound to fill, most likely in the first rain event of the year. After that, it’s overflowing until the natural spigot turns off. So as a stand-alone stormwater management tool, it just is not that effective. This is why it is critical to design your system with an adequate overflow. The typical garden hose overflow can be prone to clogging or freezing during the winter, and is usually only 1/2” in diameter at most. Depending on the area of roof that is flowing to a barrel, this could prove to be inadequate in a heavy rain event. The overflow should be sized at least 2” in diameter and directed to flow back into the downspout stand pipe or another safe disposal location, such as a rain garden, where it can soak back into the ground.

Tip 3: Quality Counts


The right way to plumb overflow

There are several common pitfalls to avoid when installing a rain barrel system. Starting out right and taking your time with installation and fittings will pay off in the long run. Since rain barrels are typically installed in-line with an existing downspout, it lives right next to the foundation of your home. Any clogs or leaky connections can cause stormwater to drain into a basement window well or into a crawl space, certainly areas we don’t want water. Setting your rain barrel or cistern on a sound, level surface and strapping it in place will help prevent any unforeseen safety issues, and increase the likelihood that, in the event of an emergency such as an earthquake, you will still have your emergency water supply to tap into.

Tip 4: Be Prepared

If you are considering a rain barrel as a backup water supply, keep the following in mind. Filtering, boiling or other purification will be needed, so have a plan of attack on how to make your rainwater potable. Water in a rain barrel or cistern can get stagnant or grow algae over the summer months, so a periodic flushing will be required. This is the perfect excuse to drain your barrel on your garden. Refilling the barrel with water you would have used on the garden will ensure it is ready to go in case of emergency.

Tip 5: Check and recheck

Rainwater harvesting systems are an active system that needs regular maintenance. Be sure you are checking your system for debris, clogs and leaks throughout the year. Leaf screens and other “first flush” devices can help prevent clogs and debris from causing issues with your rain barrel plumbing, but even these devices need regular checks and maintenance. Schedule inspections of your rainwater catchment systems with other household chores such as garbage night. This will protect your investment and ensure that your catchment system is a great amenity, and not a nuisance.


Check out the Rain Barrel Guide here.

The City of Portland has a great Rain Barrel How to Guide that I would encourage you to read. It is a step by step guide that goes into significantly greater depth and delves into the fine nuances of rain barrel installation and maintenance. Rain barrels are just the tip of the iceberg, perhaps a rain garden is also in your future? For more information on stormwater management including the rain barrel guide,
visit the technical assistance page of the Clean River Rewards website.

Happy harvesting!