Quick verdict
Two adaptors that fit over the end of a standard 3 by 4 inch rectangular downspout and convert it to a round 4 inch outlet that takes corrugated drain pipe, Flex-Drain expandable pipe or 4 inch PVC, so roof water is piped underground away from the foundation instead of dumped at the base of the wall. The joint between a downspout and a drain line is the one most people improvise with tape and a splash block; a moulded adaptor makes it a real connection. Two in the pack do two downspouts, and the fit is snug on the common 3 by 4 profile.
Strengths
- Converts a 3 by 4 downspout to a 4 inch round outlet
- Takes corrugated, Flex-Drain and 4 inch PVC
- Snug push fit; screws or tape optional
- Two per pack for two downspouts
- Rated far beyond anything a downspout sees
Weaknesses
- For 3 by 4 downspouts; 2 by 3 needs its own adaptor
- Round pipe size must match: 4 inch, not 3
- Push fit can be pulled off by a frozen pipe; secure it
The overall YardToolLab Score is out of 100. Section scores are out of 10.
The Joint Everyone Improvises
Where a rectangular downspout meets a round drain pipe is where most yard drainage goes wrong: taped, wedged or simply aimed. Flex-Drain’s adaptor is a moulded fitting that slides over a 3 by 4 inch downspout and ends in a round 4 inch outlet that corrugated pipe, expandable pipe or PVC pushes onto. Two in the pack do the two downspouts at the front of most houses.
This review is based on the maker’s specifications and on how downspout adaptors are used in buried drain lines generally. We have not fitted this adaptor ourselves.
Fitting
Cut the downspout square a few inches above the ground with tin snips, removing the elbow and the splash block. Push the adaptor up over the end until it seats and drive a short screw through its side into the metal so it cannot be pulled off. Push the drain pipe onto the round outlet, tape or clamp it, and run the pipe at a fall to its outlet. Fifteen minutes per downspout before the trench is dug.
Where the Water Goes
At least ten feet from the foundation, to a pop-up emitter on the lawn, a dry well, a swale or a slope that falls away. A downspout emptying at the wall is the most common cause of a wet basement, and this fitting is the start of the cure.
Which Pipe
Corrugated 4 inch is cheap and bends round things but holds silt in its ribs. Solid PVC runs straight and snakes clean. Flex-Drain expandable pipe does short awkward runs. The adaptor takes all three at 4 inches; a 3 inch pipe does not fit.
Build
Polypropylene that takes frost and sun at grade. The fit on a standard 3 by 4 downspout is snug and the outlet is a true 4 inch socket.
Frost
Water left in the pipe freezes and the pipe expands; an unsecured adaptor is pushed off. The screw into the downspout and a clamp on the pipe stop that.
Who Should Buy It
- Anyone burying a downspout line.
- Homeowners with a damp basement under a downspout.
- People replacing a taped joint that leaks.
Common Owner Complaints
Wrong downspout size ordered. Measure: 3 by 4 or 2 by 3.
Alternatives to Consider
The 2 by 3 version for smaller downspouts. An NDS downspout adaptor for a square-to-round in another profile. A downspout filter above the adaptor to keep leaves out of the pipe.
Verdict
For a downspout that feeds a real drain line, a moulded adaptor is the proper joint and this pair does two spouts for very little. Cut square, screw it on, clamp the pipe and send the water away from the house.
Full specifications
Flex-Drain ADP53102 Downspout Adaptor, 3 x 4 Inch Downspout to 4 Inch Corrugated or PVC Drain Pipe, 2 Pack FAQs
Cut the downspout a few inches above ground, push the adaptor onto the end, and push the 4 inch pipe onto the round outlet. A screw through the adaptor into the downspout and tape or a clamp on the pipe keep it together through frost.
Roof water dumped at the wall soaks the foundation and the basement. Piped ten feet or more to a dry well, a pop-up emitter or a slope, it leaves the house alone.
Corrugated 4 inch for a cheap run, solid PVC for a long run that will be snaked, or Flex-Drain for a short run round obstacles.
No. The 2 by 3 adaptor is a different part.
