Building a Rain Barrel System

Is rain collection allowed where I live?

Rules about collecting rainwater differ by state, county and sometimes by city or water district. Some places encourage it and some set limits or require certain setups. Before you buy anything, ask your county or state water resources office, your local building department and, if you have one, your homeowners association what applies to you.

Ask whether there are limits on barrel size, rules on how the water may be used, or permit requirements for larger tanks. Do not assume that a rule you heard from a neighbor or read elsewhere applies in your town.

How much water can my roof give me?

Collection depends on the roof area that drains to a downspout and on how much rain falls. A small roof section fills a barrel quickly in a good storm, so most systems fill and overflow often. Local rainfall data is available from your weather service or extension office.

Start with one or two barrels and add more only if you find you run out. Pairing barrels in a row lets overflow fill the next one, and the cost categories are barrels, fittings, a stand, screening and diverters.

Look at your gutters and roofing before you plan. Roofing materials, moss and heavy debris affect what ends up in the barrel, so clean gutters first and think about a first-flush device that diverts the first dirty water. Ask your extension office what suits your roof type.

What kind of barrel should I use?

Choose a food-grade or clearly identified container that has never held chemicals. A previous use you cannot confirm is a reason to pass. Dark or opaque barrels block light and slow algae. Check that the barrel has a tight lid or screened opening so children and animals cannot fall in.

Look for sturdy plastic that is rated for outdoor use and sun exposure. Avoid containers that held pesticides, petroleum or anything unknown.

• Known prior use, with no chemical residue
• Opaque to limit algae
• Lid or fine screen at every opening
• A spigot near the bottom with room beneath for a can

How do I plumb the system?

Most systems use a diverter or a cut downspout that directs water into the barrel's top. A screen at the inlet keeps out leaves and debris, and an overflow fitting sends excess water away from your foundation. Overflow planning matters, because a full barrel in a heavy storm can drive water against the house.

Set the barrel on a stable, level base, raised enough that gravity delivers water to a hose or can. A full barrel is heavy, so build a base that will not shift or sink, and keep children away from it.

Think through the weight of what you are installing. Water is heavy, and a full barrel on a weak stand can tip or collapse. Place the base on solid, level ground with gravel or pavers, and keep children away from barrels, especially open ones.

How do I prevent mosquitoes and algae?

Standing water attracts mosquitoes. Screen every opening with fine mesh and keep the lid tight, since a gap is all they need. Ask your local health department or extension office about approved ways to prevent breeding, and follow product labels if you use anything.

Algae grows with light and warmth, so keep barrels covered and in partial shade. Empty and clean them at least once a year, or whenever they smell or look off.

Is the water safe for my garden?

Roof water can pick up bird droppings, dust and chemicals from roofing materials. Many extension offices advise using it for ornamentals and soil watering and being cautious about applying it to the edible parts of crops. Ask your office what they suggest for your roof type and crops.

Do not drink rainwater or give it to livestock without proper treatment and testing. If you want to use it for animals, consult your veterinarian and local health authority. Wash produce well before eating.

What about winter and maintenance?

In freezing climates, drain barrels before hard frost, disconnect diverters and store barrels upside down or open so ice cannot split them. Clean gutters regularly, because debris carries into the barrel and clogs fittings.

Check connections each spring, replace cracked parts and make sure screens are intact. A small amount of seasonal upkeep keeps the system working for years.

Keep a short checklist for the season: clean gutters, inspect screens, check the overflow, test the spigot and look for leaks. A few minutes each spring prevents trouble when the first big storm arrives.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.