How to Choose a Downspout Diverter: Sizing, Types, and Setup

Guide

A downspout diverter must match your downspout’s shape and outside dimensions, your barrel’s inlet size, and your preferred fill method.

Most US homes run either a 2 × 3-inch or 3 × 4-inch rectangular downspout, and many kits fit one size but not the other. Measure the actual metal before you order.

What Determines Whether a Diverter Fits Your Downspout?

Downspout shape and outside measurements decide compatibility; round or custom-profile downspouts fall outside most standard kits. Fulton County’s installation guide documents its RainRecycle kit for 3 × 4-inch and 2 × 3-inch rectangular downspouts only, with no support for round pipe.

Record the outside width and depth at the height where the diverter will sit, then check three more numbers, since every kit drills its own holes:

  • Downspout hole — Fulton specifies 2⅛ inches.
  • Barrel inlet hole — 1½ inches on the same kit.
  • Spigot hole — 1¼ inches.

Hose reach is the forgotten constraint. Fulton’s fill hose spans roughly 2.5 feet, so a distant barrel may need a longer line or a closer spot. A tested roundup of diverter options can shortcut the comparison.

Factor To Check Typical Spec Why It Matters
Downspout profile Rectangular 2 × 3 or 3 × 4 inch Round and custom profiles need different hardware
Downspout hole 2⅛ inch Kit hole saws are size-specific
Barrel inlet 1½ inch Must match the diverter’s outlet fitting
Spigot hole 1¼ inch Drain fitting for emptying the barrel
Fill hose length About 2.5 feet Short hoses limit barrel placement
Barrel capacity 50 gallons typical
Overflow distance 4 feet from foundation Keeps bypass water away from the house

Which Diverter Type Suits Your Setup?

In-line automatic diverters sit on or through the downspout and send water down the hose continuously while the barrel fills; once it tops out, excess bypasses through the downspout outlet. This is the most common hands-off choice.

Cut-and-reconfigure valves mean cutting the downspout and fitting a valve or intake trough. DC’s RiverSmart cistern manual describes a control handle with a “bypass” setting that sends roof runoff straight to a porous surface when you don’t want it in the barrel. You get manual control — and a handle to remember.

Direct-discharge conversions skip the diverter: shorten the downspout and fit an elbow that dumps straight into the barrel. Rutgers recommends keeping the removed section for winter reinstallation. Simplest build, least flexible.

compare the top-rated downspout diverter kits

How Do You Install a Diverter So It Actually Fills?

Success hinges on elevation, hole placement, and a level base — drilling is the easy part. Set the barrel on compacted, solid, level ground first;

  1. Position the barrel near the downspout and dry-fit the hose with no tension, kinks, or sharp bends.
  2. Run a level across the barrel top to set diverter height.
  3. Drill the kit’s specified hole size, slowly, wearing safety glasses and gloves. File the sharp edge.
  4. Insert the diverter with its collection cup facing upward. Fulton’s instructions say push it straight in, keep the arrow up, and lock it with self-tapping screws.
  5. Connect the hose to the diverter and barrel inlet; soapy water eases a stiff hose over the fitting.
  6. Route the overflow to a permeable area at least 4 feet from the foundation, adding a diffuser where water might erode soil.

The diverter should sit flush with the arrow pointing up before you reach for the hose. Fulton County’s diverter installation guide details the hole sizes, screw placement, and height checks that prevent a leaking or non-filling system.

Keep the tubing projection inside the barrel under 2 inches and strip any slack, or the fill line sags and traps water.

Common Questions

Can I install a downspout diverter on a round downspout?

Standard rectangular kits generally won’t work on round pipe. Fulton County’s documented kit supports 2 × 3-inch and 3 × 4-inch rectangular downspouts only, so measure your profile first. For round downspouts, look for a diverter explicitly rated for that shape rather than forcing a rectangular fitting.

Does a full rain barrel stop the diverter from working?

No. In-line automatic diverters keep passing water down the downspout once the barrel fills, so runoff continues to the outlet instead of backing up. That bypass behavior is why automatic diverters are popular — no babysitting during a storm.

How high should the diverter sit on the downspout?

Set the height with a level across the barrel top. Check the kit’s instructions for its recommended elevation before drilling.

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