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Muddy flash flood wrecked my Tucson yard drainage plan | Desert Home Renovations - Vivisector

Muddy flash flood wrecked my Tucson yard drainage plan

Last August a storm dumped 2 inches in 40 minutes and my French drain just gave up. Water backed up under the patio slab and lifted two pavers clean off. I spent $1,200 on a grading contractor who told me my outlet pipe was too small and aimed wrong. Now I check the gutter downspout angles before every monsoon. Anyone else had a wash or arroyo reroute through their property after a heavy rain?

2 comments

2 Comments

evan5431mo ago

Grading contractors usually get the slope right, but the pipe size thing is where they cut corners. 2 inches in 40 minutes is a lot of water, but honestly most French drains fail because the outlet is just dumped into the yard instead of tied into a real drain or daylight. That's the part that gets overlooked. The last big storm here showed me that even a 4 inch pipe clogs fast if you don't have a cleanout right at the turn. Your pavers lifting is rough though, that means the compacted base under them got saturated, not just the drain issue. Maybe check if your downspouts are actually far enough from the slab too, that's a cheap fix compared to another contractor visit.

mason_reed471mo ago

Wait, did the contractor actually check the outlet pipe slope before calling it too small, or just the size? @evan543 makes a good point about cleanouts at turns, but I'd also add that checking the pipe for any low spots or sags after the soil settles is huge. One year after my install, a dip formed right where the trench crossed the old utility line, and water pooled there instead of draining. If your pavers lifted, that suggests the base is shot too, so even if you fix the pipe, the ground might shift again. Maybe grab a cheap level and walk the whole drain line after a dry week, see if there's any standing water hiding in sections you can't see. Also, the downspout extension thing is real, I got 10 feet of corrugated pipe at the hardware store for like 15 bucks and moved my outlet way past the slab. That alone stopped most of the patio pooling.