Guide · Drainage for Arizona Yards
Backyard drainage decision guide — diagnose the source, then pick the right system.
Most drainage articles jump straight to 'install a French drain.' That's why so many Valley drainage installs fail in the first two monsoons. The correct sequence is: find where the water originates, decide whether it's surface flow or subsurface, confirm a legal discharge, then pick the collection method that matches. This guide walks through AE's diagnostic sequence, when each tool is right (and when it's not), how neighboring properties and pool overflow complicate the picture, and real Valley investment ranges.
The honest version: A French drain is the wrong answer for the vast majority of Phoenix backyards — the water is surface runoff, not groundwater, and desert clay and caliche don't perc. If a contractor bids a French drain without walking your grade during rain or running a hose test, they're guessing. AE won't install a drain we don't believe will still be working in year five.
01
Step 1 — Diagnose where the water actually originates
- Walk the yard during or immediately after a monsoon when possible — the only time you see real flow
- Between storms, run a hose test at suspected origins and follow the path
- Check every source: roof valleys, downspouts, neighbor high-side, HVAC condensate, pool overflow, irrigation heads
- Read the grade with a laser level, not by eye
- The problem is almost always 20–60 ft upslope from where the water is standing
- Fixing the puddle without finding the source guarantees a callback
02
Step 2 — Surface drainage vs underground drainage
Surface drainage (grading, swales, hard-surface slope) is always first choice when the grade allows — cheaper, self-cleaning, and doesn't clog. Underground drainage (basins, channel drains, solid pipe) is used when grade is fixed by house, hardscape, or property lines. The best systems combine both: shape the yard to shed water toward defined collection points, then use pipe to route it to a legal discharge. Underground-only systems silt up in the Valley because they carry desert dust and mulch fines.
03
When a channel drain is the right choice
- Sheet flow crossing a hard surface at a defined line
- Garage apron, walkway between patio and pool, driveway meeting courtyard, low edge of a large patio
- Linear interception across a span, not a single point
- Requires downhill outlet — a channel drain plumbed into a dead-end pipe is worse than no drain
- Wrong tool for turf, planters, or area collection
04
When a catch basin is the right choice
- Point collection at a definable low spot — bottom of a bowl in lawn, corner where two grades meet
- You can slope surrounding grade toward it
- Size for peak flow — undersized basins overflow in monsoon burst
- AE typical: 9" or 12" basin, 4" solid SDR pipe to legal discharge
05
When a French drain will NOT work
- Heavy clay soil that won't let water percolate into the trench
- Caliche layer above or below the pipe blocking flow
- Trench dug flat instead of sloped
- No filter fabric — fines silt the gravel within a season
- Outlet higher than the trench low point (physics doesn't care about your bid)
- Real problem is surface runoff, not groundwater — most Valley yards
- Bottom line: French drains are misused constantly in Phoenix. Use a catch basin and solid pipe.
06
Discharge — where you can legally send the water
- Never across a property line onto a neighbor's yard — actionable
- Never into sanitary sewer or a sewer cleanout
- Front-yard pop-up emitters often prohibited by HOA
- Street or right-of-way discharge — often allowed via curb-cut, sometimes requires city approval
- Wash or public retention basin — usually allowed with proper tie-in
- Some subdivisions require all site water retained on-lot
- AE checks city and HOA before designing the outlet — not after
07
Dry wells and on-lot retention
A dry well is a large gravel-filled or chambered pit that lets collected water percolate into the subsoil over hours or days. Use one when you have significant volume and no legal discharge — retention lots, tight infill, some HOAs. Sizing is based on peak inflow AND soil percolation rate; caliche sites need much larger wells because the surrounding soil percs slowly. Undersized dry wells back up in monsoon and dump water back into the yard. On-lot retention means the site holds a designed storm volume (often the 100-year 2-hour event) — many Valley subdivisions built after the late '80s designed the low corner of the backyard as the retention basin. Filling it, paving it, or building on it violates the drainage report. Always identify the platted retention area first.
08
How pool overflow affects drainage
- Every pool in a monsoon fills above the skimmer and dumps over coping to the deck
- Design assumption: your pool overflows 2–4 times a summer
- Deck grade must move that water away from the pool, off the deck, to a channel drain or scupper
- Never toward the house, equipment pad, or low-side patio furniture
- AE designs an autofill overflow line on new pools so day-to-day overfills go to a controlled discharge, not the deck
09
How neighboring properties complicate grading
- Older Valley neighborhoods were graded as a block-wide system — cutting off high-side neighbor's water can flood them
- Your yard may be a required input to the low-side neighbor's swale
- Drainage easements on the plat cannot be altered without violating it
- Common problems: neighbor's new pool now dumps into your yard; neighbor's new wall backs water up on your side; neighbor's downspout aims across the fence
- AE reads adjacent grades before designing and documents pre-existing condition in writing
10
Why so many Valley drainage jobs fail in two years
- Installer never diagnosed the true water source
- Undersized pipe or basin for peak monsoon flow
- No cleanouts at bends or at 90 ft intervals — silt clogs the line permanently
- Discharge to a non-existent 'daylight' that's actually flat or uphill
- Surface grade wasn't corrected — the drain fights the grade forever
- Our fix rate on other people's drainage work is high because these mistakes are consistent
11
Typical drainage-correction investment ranges — Valley numbers
- Single catch basin + 30 ft of 4" pipe to curb pop-up — from ~$1,800
- Multi-basin backyard system, two collection points, 60–100 ft of pipe — $4,500–$9,000
- Full backyard regrade with swales, three basins, patio channel drain, street discharge — $9,000–$22,000
- Dry well install with 4-ft-diameter chamber and inflow plumbing — $3,500–$7,500
- Complete drainage master plan (regrade, retention resize, pool-deck channel, multi-outlet) — $18,000–$45,000
- All ranges published — never 'call for pricing'
12
AE's drainage decision sequence
- 1. Diagnose the source with a rain walk or hose test — never guess
- 2. Read the grade with a laser and document neighbor conditions
- 3. Identify a legal discharge (street, wash, on-lot retention, dry well)
- 4. Correct surface grade first — swales and slope before pipe
- 5. Add underground collection only where surface can't reach the outlet
- 6. Match tool to problem: channel drain for linear sheet flow, catch basin for point collection, dry well when there's no outlet
- 7. Include cleanouts, filter fabric where appropriate, and pipe sizing for peak monsoon flow
- 8. Pull the permit if the work crosses public right-of-way or alters platted grading
FAQ
Common questions.
AE walks the yard during or immediately after a monsoon whenever possible — that's the only time you see the real flow. Between storms, we run a hose test at suspected origins (roof valleys, downspouts, neighbor high-side, HVAC condensate, pool overflow, irrigation heads) and watch where water travels and pools. We also read the grade with a laser level, check roof drainage exits, and inspect any existing drain inlets. Nine times out of ten, the problem isn't where the water is standing — it's 20–60 feet upslope. Fixing the puddle without finding the source guarantees a callback.
Channel drains work when you have sheet flow crossing a hard surface at a defined line — a garage apron, a walkway between the patio and pool, a driveway meeting a courtyard, or the low edge of a large patio. They intercept water across a linear span rather than a single point. They do not work for area collection in turf or planted beds, and they only work if there's somewhere for the water to go downhill from the channel outlet. A channel drain plumbed into a dead-end pipe is worse than no drain.
Catch basins collect water at a low point — the bottom of a bowl in the lawn, an area between planters, a corner where two grades meet. They're point collection, not linear. Use them when water pools in a definable spot and you can slope the surrounding grade toward it. Size and depth depend on peak flow — undersized basins overflow in a real monsoon burst. AE typically pairs a 9" or 12" basin with 4" solid SDR pipe to a code-legal discharge.
French drains are perforated pipe in gravel that collects subsurface water. They fail — every time — in these conditions: (1) heavy clay soil that won't let water percolate into the trench, (2) caliche layer above or below the pipe blocking flow, (3) the trench is dug flat instead of sloped, (4) no filter fabric so fines silt the gravel within a season, (5) the outlet is higher than the trench low point, or (6) the real problem is surface runoff, not groundwater. For most Valley backyards the water is surface flow, not subsurface, and a French drain is the wrong tool. Use a catch basin and solid pipe instead.
Surface drainage (grading, swales, hard-surface slope) is first choice whenever the grade allows — it's cheaper, self-cleaning, and doesn't clog. Underground drainage (basins, channel drains, solid pipe) is used when the grade is fixed by the house, hardscape, or property lines and water can't be moved with surface slope alone. Best systems combine both: grade the yard to shed water toward defined collection points, then use underground pipe to route it to a legal discharge. Underground-only systems in the Valley silt up because they carry desert dust and mulch fines.
Rules vary by jurisdiction, but the constants: (1) never discharge across a property line onto a neighbor's yard — that's actionable, (2) never discharge into the sanitary sewer or a sewer cleanout, (3) many HOAs prohibit visible pop-up emitters in the front yard, (4) discharge to a public street or right-of-way is often allowed via a curb-cut but sometimes requires city approval, (5) discharge into a wash or retention basin is usually allowed if you tie in properly, (6) some subdivisions require all site water to be retained on-lot. AE checks the city and HOA before designing the outlet, not after.
A dry well is a large gravel-filled or chambered pit that lets collected water percolate into the subsoil over hours or days. Use one when you have significant volume and no legal discharge location — retention lots, tight urban infill, some HOAs. Sizing is based on peak inflow and soil percolation rate; caliche-heavy sites need much larger wells because the surrounding soil percs slowly. Undersized dry wells back up during monsoon and dump water back into the yard. AE sizes wells with a percolation test, not a guess.
On-lot retention means the site must hold a designed storm volume (often the 100-year 2-hour event) inside the property lines — no discharge to the street or neighbors. Many Valley subdivisions built after the late '80s were designed this way, and the retention basin is sometimes the low corner of the backyard by design. Filling it in, paving over it, or adding a structure inside it violates the drainage report and can create liability. Always identify the platted retention area before designing anything in that corner.
Every pool in a monsoon fills above the skimmer during a hard rain, then dumps water over the coping to the deck. Design assumption: your pool will overflow 2–4 times a summer. The deck grade must move that water away from the pool and off the deck to a channel drain or scupper — not toward the house, not toward the equipment pad, and not into low-side patio furniture. AE also designs an autofill overflow line on new pools so day-to-day overfills go to a controlled discharge, not the deck.
In older Valley neighborhoods, the entire block was graded as one system — cutting off the water from your high-side neighbor can flood their yard, and their water may be a required input to your low-side neighbor's swale. In HOA subdivisions with drainage easements, you cannot alter the easement grade without violating the plat. Common problems: neighbor added a pool and their new grading now dumps into your yard; neighbor built a wall on the property line and now water backs up on your side; neighbor's downspout aims across the fence. AE reads adjacent grades before we design, and we document the pre-existing condition in writing.
Real Arizona ranges, fully installed: single catch basin + 30 ft of 4" pipe to a curb pop-up — from ~$1,800. Multi-basin backyard system with two collection points and 60–100 ft of pipe — $4,500–$9,000. Full backyard regrade with new swales, three catch basins, channel drain across a patio, and legal street discharge — $9,000–$22,000. Dry well install with 4-ft-diameter chamber and inflow plumbing — $3,500–$7,500. Complete drainage master plan with regrade, retention resize, pool-deck channel, and multi-outlet — $18,000–$45,000. We publish ranges — never 'call for pricing.'
Five reasons we see over and over: (1) the installer never diagnosed the true water source, (2) undersized pipe or basin for peak monsoon flow, (3) no cleanout at bends or at 90 ft intervals, so silt clogs the line permanently, (4) discharge to a non-existent 'daylight' that's actually flat or uphill, (5) surface grade wasn't corrected — the drain fights the grade forever. AE's fix rate on other people's drainage work is high because these mistakes are consistent.
Water in the wrong place? Let's find the source first.
Send photos during or after rain if you can. AE will diagnose the origin, propose the right system (not a default French drain), and give you a real Valley investment range.
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Why this is an investment, not a cost.
An AE backyard is engineered to add daily livability and long-term home value. We publish honest ranges and build to code with a licensed and bonded Arizona crew. AE provides project-specific workmanship and manufacturer-warranty information in the signed agreement. Website summaries are for planning only.
- Licensed, bonded & insured in Arizona. ROC 340966 (R-62) · ROC 341002 (R-3) · ROC 347738 (KA-5) · ROC 211530 (CR-21). Most Arizona contracting work valued at $1,000 or more — or requiring a permit — must be performed by a properly licensed contractor, subject to statutory exemptions. Verify the legal entity, license status, and classification with the Arizona Registrar of Contractors.
- Real ranges, itemized scope. You see materials, finishes, equipment models, and a line-item budget before you sign — not a one-line "pool — $90,000."