How We Built Our Gravity-Fed Water System for $400

The Setup — What We Were Working With

The core of this system is a 500-gallon HDPE tank mounted on a timber stand 28 feet above the cabin floor. That elevation is everything: 28 feet of head pressure translates to 12.1 PSI at the cabin (28 ÷ 2.31), which is enough to run a kitchen sink and bathroom faucet without a pressure tank or pump in the picture.

The tank feeds from a spring-fed collection box on the hillside, 180 feet away and roughly 15 feet higher than the tank itself. The spring does the work of filling; gravity does the work of distributing. There is no pump anywhere in this system — not at the spring, not at the tank, not at the cabin.

We plumbed three distribution points: kitchen sink, bathroom sink, and an outdoor wash station. We skipped an indoor shower intentionally — we use an outdoor solar shower, and the pressure is marginal enough that a showerhead would be disappointing indoors anyway. Total material cost for everything from tank to faucets: $398.

The Full Materials List

Building the Tank Stand

We built the stand from four 4×4 treated lumber posts at 8 feet above grade. The natural slope of the hillside provides the remaining 20 feet of effective elevation above the cabin floor. Double 2×8 beams span the top, with 2×6 diagonal braces on all four sides for lateral rigidity.

The load math: 500 gallons × 8.34 lb/gal = 4,170 lbs of dead load when full. We designed the stand for significantly more than that. When a structure is holding 2+ tons over your cabin, over-engineering is the correct call.

Mistake we made: We didn’t account for the uneven load when the float valve closes and water fills from one side of the tank. The float valve side pulled the tank slightly off-level — not dangerously, but enough to matter. We added a diagonal corner brace after the fact. The fix took an afternoon. The lesson: install all bracing before the tank goes up, not after.

Plumbing the System

We ran 1″ polyethylene from the tank outlet, reduced to a 3/4″ main line at the base of the stand, then branched to 1/2″ at each fixture. Larger diameter at the tank, smaller at the taps — that sizing progression helps maintain velocity and minimizes pressure drop across the run.

Before the distribution tee inside the cabin, we installed a 20-micron sediment filter housing. Spring water is cleaner than well water in most cases, but fine sediment and particulates still work their way through. The cartridge is cheap insurance.

Measured pressure at the kitchen sink: 10.8 PSI. Our calculation predicted 12.1 PSI, so we lost 1.3 PSI to friction across the 150-foot run — right in line with expectations. The float valve in the tank handles refill automatically: as the tank drains, the valve opens; as the spring replenishes it, the valve shuts. We have never manually intervened in that process.

Six Months of Operation — What Works, What Doesn’t

Works Well

• Zero maintenance on the pipe runs in 6 months
• Sediment filter: replaced once in 6 months (spring water is relatively clean)
• Flow rate at kitchen sink: fills a 1-gallon pot in 90 seconds — adequate for all cooking and washing
• The spring has never run low — output comfortably exceeds demand year-round

What We’d Do Differently

• Better spring collection box: the screened inlet needs a finer screen — insects got into the tank during summer
• Second shutoff valve at the house entry: currently have to hike to the tank to fully shut off water; an inline ball valve at the cabin entry would fix this
• Upsize the main pipe to 1″: 3/4″ main is borderline when kitchen and bathroom sinks run simultaneously; noticeable pressure drop

Water Quality

We had the spring water tested before we committed to drinking it. Results: zero coliform bacteria, pH 7.2, hardness 145 mg/L. That hardness reading puts it in the moderately hard range — noticeable in a kettle over time, but not a problem for washing or bathing. No pathogens, no treatment required for non-potable use.

For drinking and cooking, we added a Big Berkey gravity filter at the kitchen counter. The Berkey handles bacteria, heavy metals, and chlorine by gravity alone — no electricity, no replacement membranes, just two black filter elements that last years. The spring water tastes genuinely good through it. One-time cost: $285. We consider it a permanent part of the kitchen, not a backup device.

Complete Water System Cost Summary

$748 for a complete, full-time water supply for two people — kitchen, bathroom, washing. No electricity draw. No pump to maintain or replace. No pressure tank sitting in a utility room. The only recurring cost in six months has been one sediment filter cartridge.

More Detailed Guides

• Gravity Water System Guide — the technical deep-dive on pressure, pipe sizing, and tank placement
• Water Filtration Guide — choosing the right filter for your water source
• Big Berkey Review — our drinking water filter