40,000 Gallons of Off-Grid Water Security in the Arizona Desert

Build Overview

When Derek Howlett purchased land in the Sulphur Springs Valley of southeastern Arizona, he faced the water challenge confronting many rural Arizona landowners: groundwater levels are declining, well drilling is expensive and uncertain, and hauling water is unsustainable long-term. His answer was to build one of the most thoroughly documented large-scale residential rainwater harvesting systems in the American Southwest.

By March 2023, Howlett had accumulated 40,000 gallons of total rainwater storage across his property — enough to supply a household's complete water needs for well over a year without a single drop of rain. This case study documents the complete system: tanks, catchment surface, pump house, filtration, treatment, and the financial logic of doing it in phases.

"Let's do this right, so we only have to do it once." — Derek Howlett, Handeeman

Howlett's approach is not a hobbyist experiment. Handeeman Contracting is a legitimate rainwater systems business recognized by the University of Arizona Cooperative Extension as a reference example for large-scale potable rainwater harvesting. His own property is his most visible portfolio piece.

The Case for Rainwater in Arizona

The counterintuitive argument of this build is its most persuasive element: if you can build a 40,000-gallon rainwater system in one of the drier parts of the American Southwest, you can build one almost anywhere. Understanding why it works in Arizona is the foundation for evaluating any large-scale rainwater system.

Arizona's Bimodal Rainfall Pattern

Most of Arizona receives rainfall in two distinct seasonal windows. Winter rains (December–February) are driven by Pacific weather systems — typically gentler, longer-duration events that allow good catchment efficiency. The summer monsoon (July–September) delivers intense convective storms that can drop 1–3 inches in a single event. Cochise County averages 12–19 inches annually depending on elevation.

The critical implication: dry periods can be long, and when rain comes it often arrives hard and fast. A system designed to catch monsoon events needs large-capacity storage to bank the water from intense events for use through dry months. This is exactly what Howlett's 40,000-gallon system is designed for.

Why Not a Well?

The University of Arizona Cooperative Extension study that cites Howlett's property documents the economic and reliability drivers behind the choice of rainwater over groundwater:

• Aquifer overdraft: Groundwater levels in the Sulphur Springs Valley and many Arizona basins are declining year over year. Wells drilled to adequate depth today may be insufficient within a decade.
• Drilling cost and uncertainty: Well drilling in Arizona runs $5,000–$30,000+ depending on depth and geology, with no guarantee of finding adequate water.
• Water quality: Arizona groundwater is frequently high in dissolved minerals, arsenic, or other contaminants. Rainwater starts chemically clean.
• Reliability inversion: In declining aquifer regions, rainwater is not the alternative — it is the reliable option. A properly designed rainwater system has no declining water table.

The Collection Math

The University of Arizona Cooperative Extension documents the formula used by practitioners like Howlett:

Applied to Howlett's 4,675 sq ft garage roof in Cochise County, using 15 inches annual rainfall as a conservative mid-point:

4,675 × 15 × 0.623 × 0.85 = ~37,200 gallons per year

With additional catchment from the house roof and other structures, Howlett's 40,000-gallon storage capacity is designed to be fully replenished at least once annually — meaning the system is sustainable as a primary water source, not just a backup. A 1-inch rain event on the garage roof alone produces approximately 2,900 gallons. A 2-inch monsoon storm delivers nearly 5,800 gallons in a single event.

The Tank — Aquamate Corrugated Steel with NSF Liner

The centerpiece of the system is a 28,000-gallon Aquamate corrugated galvanized steel tank, installed in 2019 as Phase 1. The choice of Aquamate reflects a specific set of trade-offs that any large-scale rainwater system builder must navigate.

Aquamate Tank Sizing & Pricing

Handeeman Contracting serves as an authorized Aquamate installer covering within 125 miles of Benson, AZ. The pricing below (2023–2024) includes delivery and installation — the one-day assembly is a signature advantage of Aquamate's modular panel system.

The Catchment Surface

The primary catchment is the roof of an 85' × 55' multi-use garage and workshop — 4,675 square feet. This is the most important infrastructure decision in any rainwater harvesting system: the catchment surface determines your annual supply ceiling. No amount of storage capacity helps if you can't collect enough water to fill it.

Why a Metal Roof Is the Correct Choice

The University of Arizona Cooperative Extension guide that cites Howlett's property is explicit about roof materials for potable collection. Standing seam metal roof (Howlett's choice) is the recommended standard: no coatings to leach, smooth for runoff, and compatible with NSF-certified liner tanks without chemical interaction concerns. See the roof material table in the hub guide for a full comparison.

Gutter Sizing for Peak Flow

A 4,675 sq ft roof in a monsoon environment produces roughly 2,900 gallons from a 1-inch rain event. A 2-inch storm — not unusual in Arizona monsoon season — delivers nearly 5,800 gallons in a matter of hours. Gutter and downspout sizing must handle this peak flow without overtopping:

• 6-inch K-style or box gutters (not residential 4-inch) on a building this size
• Multiple downspouts distributed along the roof length — no single point overwhelmed in a high-intensity event
• Leaf guards and coarse inlet screens at gutter entrances
• Underground wet delivery pipe from building to tank — self-primes immediately when rain starts

First Flush Diversion — The Overlooked Foundation of Water Quality

After a dry period, a roof surface accumulates bird droppings, dust, pollen, atmospheric particulates, and organic debris. When rain begins, the first flow of water washes all of this contamination off in concentrated form. Without diversion, this water enters the tank — and no post-tank treatment works as well as simply keeping that contaminated water out in the first place.

How It Works

• A standpipe installed in the downspout run fills with the first, most contaminated flow of each rain event
• Once full, a floating ball rises to seal the inlet; subsequent cleaner water bypasses the chamber and flows to the tank
• A slow-release drain at the standpipe bottom empties it between rain events, resetting it for the next storm
• Sizing rule: divert 1 gallon per 100 sq ft of catchment area per rain event

For Howlett's 4,675 sq ft roof, a properly sized first flush system diverts approximately 47 gallons before allowing water into the tank — a small sacrifice for dramatically improved water quality across the entire season's harvest. Skip it and the entire post-tank treatment train works harder for worse results.

The Pump House — Centralizing the Mechanical Heart

One of the most instructive elements of Howlett's build for other system designers is the dedicated pump house: a small outbuilding adjacent to the tank that houses all mechanical, electrical, and filtration components. This is not a luxury — it is a maintenance and longevity decision.

What Lives in the Pump House

• Pump: Submersible (in tank) or surface pump (in pump house) — draws water from the tank and pressurizes the distribution system
• Pressure tank: Bladder tank maintains system pressure between pump cycles; prevents the pump from short-cycling every time a faucet opens
• Pre-filtration: 5-micron sediment cartridge filter removes fine particles that passed the inlet screen
• Carbon block filter: Removes taste and odor compounds — particularly important for water stored in warm tanks during Arizona summer
• UV disinfection unit: The primary kill step for bacteria, viruses, and protozoa; requires pre-filtration to clear turbidity before UV exposure is effective
• Pressure gauges, shut-off valves, bypass plumbing: Allow servicing of any component without shutting down the entire system
• Electrical panel: Powers pump and UV unit; in an off-grid system, supplied by solar and battery

Why a Dedicated Pump House Matters

• Climate protection: UV exposure degrades plastic fittings and filter housings; Arizona summer temperatures exceed 110°F. An enclosed pump house extends equipment life significantly.
• Security: A lockable enclosure prevents tampering with the water supply.
• Maintenance access: A dedicated structure makes filter changes and troubleshooting straightforward rather than a crawl-through exercise.
• Aesthetics: All mechanical equipment is concealed — the tank is the only visible system element.

Treatment Train — Making Harvested Rainwater Safe to Drink

Rainwater is not inherently safe to drink without treatment. While it starts cleaner than groundwater — free of minerals, arsenic, and Arizona groundwater contaminants — it can accumulate biological contamination from roof surfaces and storage. Howlett's system includes the multi-stage treatment sequence standard for potable rainwater use.

Building in Phases — The Financial Logic

Rather than building the entire 40,000-gallon system at once, Howlett's build evolved over several years. This phased approach is not just a convenience — it is a rational financial strategy.

Phase 1 (2019) — 28,000-Gallon Foundation

• 28,000-gallon Aquamate tank delivered and assembled on-site in a single day
• Pump house constructed to house all mechanical components
• Primary catchment (4,675 sq ft garage roof) plumbed with underground wet delivery system
• First flush diversion and inlet filtration installed at tank entry
• Basic treatment train (sediment + carbon + UV) commissioned
• Capital cost: ~$16,225 for the tank installed, plus pump house and treatment

Phase 2+ — Expanding to 40,000 Gallons

• Additional Aquamate tank(s) added as budget and operational data dictated
• Secondary catchment surfaces (house roof, additional structures) plumbed into the system
• Aquamate Rainsaver gutter system fitted to tank roofs to capture rainfall directly on the tank surface

What 40,000 Gallons Actually Means

For Howlett's household, 40,000 gallons represents well over a year of complete water independence. With annual harvest potential of ~35,000–40,000 gallons from existing catchment surfaces, the system is designed to be self-sustaining across normal weather cycles — drawing down the tank through dry months and replenishing it during monsoon season.

Arizona Regulatory Framework

Arizona is one of the most rainwater harvesting-friendly states in the US. No permit is required for most residential systems regardless of tank size, and the state actively encourages the practice as a groundwater conservation strategy.

• No permit required for most residential rainwater harvesting systems in Arizona, regardless of tank size, under current state law
• Arizona Revised Statutes §45-801 et seq. explicitly recognize the right to collect and use rainwater for beneficial use
• 25% tax credit (up to $1,000) available for installation of a water conservation system in an Arizona residence — rainwater harvesting systems qualify
• Cochise County (Howlett's location) has no additional permit requirements beyond the state framework
• For potable use, treatment to drinking water standards is a practical requirement; UV disinfection and multi-stage filtration are the standard

Key Lessons for Every Rainwater System Builder

• Storage size is the investment that enables everything else. A 5,000-gallon tank in Arizona provides weeks of supply. A 28,000-gallon tank provides years. The per-gallon cost falls dramatically as tank size increases — the economic case for going large is compelling when you're already committing to a system.
• The catchment surface is as important as the tank. Howlett's 4,675 sq ft metal roof produces more water per year than most households consume. Without adequate catchment connected properly to the tank, storage capacity is wasted.
• First flush diversion is not optional for potable systems. It's the single highest-impact water quality intervention in the system — and it costs pennies relative to the rest of the build.
• A dedicated pump house is worth building. Equipment life in Arizona's climate is significantly extended by housing mechanical components in a protected enclosure. It also makes the system far easier to maintain over years and decades.
• Phased builds are financially rational. Starting with a large primary tank and expanding based on real operational data is smarter than trying to engineer the perfect final system on day one.
• UV disinfection is the minimum viable potable treatment. Combined with sediment and carbon pre-filtration, a properly sized UV unit makes harvested rainwater safe for all household use. Arizona Extension confirms this standard.
• In declining aquifer regions, rainwater is the reliable option. Wells in the Sulphur Springs Valley are less reliable today than they were 20 years ago. A properly designed rainwater system has no declining water table.