Downspouts and drainage in Austin
We install and move downspouts and the drainage at their base, using extensions, splash blocks, and buried lines to carry roof water away from your foundation.
Downspout size and placement
A downspout has to carry everything its stretch of gutter collects, so we size it for that run. 5-inch gutters take 2x3-inch downspouts, and 6-inch gutters take 3x4-inch downspouts. We space downspouts so no run carries more water than its outlet can drain, using the rules of thumb in our gutter and downspout sizes guide.
Extensions and splash blocks
An extension or a splash block moves water out from the base of the wall, and a sloped concrete splash block spreads it and sends it away from the house. The 2021 International Residential Code calls for roof water to reach the ground at least 5 feet from the foundation where soils are expansive or collapsible. Texas law bars diverting surface water in a way that damages a neighbor’s property by overflow. The sizing guide gives the code’s wording under where downspouts can drain and cites the Texas statute.
Buried lines and pop-up emitters
Where an extension would cross a walk or a mowed lawn, the water can go underground. We trench from the downspout to a spot where the ground slopes away from the house and lay solid pipe in the trench. The line ends at a pop-up emitter that sits flush with the grass and opens when water flows. The lawn goes back over the trench.
Rain barrels and tanks
We connect downspouts to rain barrels and tanks by fitting the diverter and the run from the downspout to the tank. We don’t sell or install the tanks themselves. Our rainwater collection in Austin guide covers Austin Water’s rebate and the state rules.
What drainage costs
HomeGuide’s downspout cost guide (dated November 2025) puts an underground downspout drainage system at $150 to $350 per downspout on average. The cost guide has more on downspout costs.
Questions about downspouts and drainage
How far should a downspout extension reach?
A downspout extension should reach far enough for water to land on ground that slopes away from the house. The 2021 International Residential Code sets 5 feet from the foundation where soils are expansive or collapsible, and the sizing guide has the rest.
Can you move a downspout?
Yes, we can move a downspout. We cut a new outlet where the water should drop, seal the old one, and run the downspout to better ground.
Can a downspout drain into a rain barrel?
Yes, we can route a downspout into a rain barrel. We fit a diverter on the downspout and run it to your barrel or tank, with overflow carried away from the house.