Track 3: Water

16 diagrams.

FirstFlushStages

A first-flush diverter fills with the dirtiest water from each rain, then lets cleaner water pass to the tank.

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Three side views of the same downspout, first-flush chamber and tank. Stage 1, rain starts: water from the roof runs down the downspout and fills a vertical chamber with the first, dirtiest water, which carries dust, pollen and bird droppings. Stage 2, the chamber is full: cleaner water now passes along the side pipe into the storage tank, and the tank level rises. Stage 3, after the rain: a small opening at the bottom lets the chamber drain slowly, so it is empty and ready for the next rain. Screens and the diverter need cleaning every few weeks in the rainy season.

FrostLine

Water lines buried below the frost line stay unfrozen. How deep that line sits depends on where you live.

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Left, a section through the ground at one site, not to scale. The top layer of soil freezes in a hard winter; its lower edge is the frost line, shown as a dashed line. A water pipe inside the frozen layer can freeze and split. A water pipe buried below the frost line stays unfrozen. A note says your local building department knows your frost depth. Right, a comparison of frost depth across the lower 48 states: almost nothing in the far South, and about 5 feet (1.5 meters) in the coldest parts.

GravityPressure

Height alone makes pressure, but slowly. A tank 20 feet up gives a garden hose; household pressure needs a tank about 90 feet up, so most homes use a pump.

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Left, a sketch of a water tank on a hill above a house, with the height measured from the water surface in the tank down to the tap. Right, a chart of pressure against that height. The line rises about 0.43 psi for each foot, or about 2.3 feet for each psi. A tank 20 feet (6 meters) above the tap gives about 9 psi, enough for a garden hose or a slow tap. Getting about 40 psi takes about 90 feet (27 meters) of height. A shaded band from about 40 to 60 psi marks where many homes run.

GreyAndBlackwater

Greywater can go to mulch basins through a diverter valve. Toilet water always goes to the septic system or sewer, and kitchen water depends on local code.

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A flow diagram. Greywater comes from the shower and bath, the bathroom sink and the clothes washer. It flows to a diverter valve. Most of the year the valve sends it to mulch basins around trees and shrubs, delivered below the mulch, used within about 24 hours, never sprayed and never left to pool. In wet seasons, or for loads with bleach, the valve switches the flow to the septic system or sewer. The kitchen sink is counted as blackwater by many codes, so whether it can join the greywater depends on local code; here it goes to the septic or sewer. Toilet water is blackwater and always goes to the septic system or sewer, which needs a permit and a licensed designer.

IndoorWaterShares

Where indoor water goes in a typical US home. Toilets, showers and faucets are most of it, and leaks are a bigger share than most people expect.

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A single bar split into shares of indoor water use in a typical US home, from largest to smallest. Toilets are about a quarter. Showers are about a fifth. Faucets, for sinks, cooking and drinking, come next, then the clothes washer. Leaks are about a tenth or a bit more, and are shaded to stand out. Baths and the dishwasher are the smallest share. A note says the widths are approximate, because shares vary between studies and homes.

MulchBasin

A mulch basin. Greywater comes out below the mulch surface and soaks into the soil around a tree, where soil life breaks it down.

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A section, not to scale. A pipe from the shower or laundry runs underground from the house to a shallow basin dug around a fruit tree. The basin is filled with wood-chip mulch. The pipe ends below the mulch surface, so greywater never sprays into the air or sits on top. The water soaks down into the soil, where soil life breaks it down and the tree's wide roots take it up. Notes give the common rules: use greywater within about 24 hours, deliver it below mulch or soil, allow no sprays, pooling or runoff, and keep it off root crops and leafy greens.

PerPersonWaterUse

Per person, a water-conserving household often uses less than two-thirds of the US average, and sometimes about a third.

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A bar chart of water used at home per person per day, on a scale from 0 to 100 gallons. The US average, from the EPA, is about 80 gallons (300 liters). A water-conserving household, as given in the Texas rainwater manual, uses about 25 to 50 gallons (95 to 190 liters), shown as a range. A note says some careful households use less, and the number depends on fixtures and habits.

PumpAndPressureTank

A pump pushes water to the house, and a small pressure tank with an air cushion keeps it under pressure, so the pump does not start every time you open a tap.

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A block diagram. Water flows from a storage tank or well to a pump. The pump needs electricity, and choosing and wiring it is work for a pump contractor and a licensed electrician. From the pump, water flows into a pressure tank, which has an air cushion above the water. The squeezed air keeps the water under pressure. From the pressure tank, water flows to the taps in the house. The pump runs now and then to refill the pressure tank, rather than every time a tap opens.

RainfallPattern

Two places with the same 30 inches a year. Place B gets almost nothing in summer, so its tank has to carry the household for months.

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Two bar charts of monthly rainfall, each adding up to 30 inches (760 millimeters) a year. The numbers are illustrative. Place A gets rain most months, about 2 to 3 inches each month. Place B gets 4 to 5.5 inches a month in winter, and almost none from June to August, which are marked as the dry summer. The yearly total is the same, but the monthly pattern is very different.

RoofFootprint

Rain falls straight down, so a roof catches rain over its footprint, the area it covers seen from above, not over its sloped surface.

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Side views of two houses of the same width. The left one has a steep roof and the right one a low-slope roof. Rain falls straight down on both. Dashed lines rise from each eave to show that each roof intercepts only the rain falling inside its footprint. Under each house, a dimension line marks the footprint, measured at the outer edge of the eaves. Because the footprints are the same, both roofs catch about the same amount of rain.

TankBalance

Running the tank month by month. It overflows in the wet months and first runs empty in August. That month, not the yearly total, sets the plan.

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A line chart of the water level in a rain tank at the end of each month, from January to December, with illustrative values. The tank is full from January to April, and extra rain overflows and is lost; these months are marked as overflow. The level falls slowly in May, then quickly in June and July as rain drops and the garden needs water. The tank first runs empty in August and stays empty in September; these months are shaded as shortfall. It starts to refill in October and is nearly full again by December.

TreatmentTargets

What each method mainly deals with. No single method covers all three kinds of problem.

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A table of treatment methods against three kinds of problem: germs (pathogens), dissolved chemicals, and particles. Boiling mainly targets germs, in one pot only, and can concentrate chemicals. UV light mainly targets germs and needs clear water and electricity. Chlorination mainly targets germs, keeps working in pipes, and needs careful dosing. A sediment filter mainly targets particles; it protects later steps and helps UV work. Activated carbon deals with some chemicals, such as those that cause taste and odor and some pesticides, but not nitrate. Reverse osmosis mainly targets dissolved chemicals such as nitrate, arsenic and salts, and also blocks many germs, though it is not usually relied on as the only germ barrier; it is often used at one tap. A water softener deals with hardness minerals only and is not a safety step.

TreatmentTrain

Treatment as a series of barriers, with a test before and after. Each step targets a different kind of problem.

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A concept diagram, not a design. Water flows from the source, such as a well, spring or rain tank, to a test checkpoint: test first with a certified lab. Then it passes three treatment steps in a row. A sediment filter catches particles and grit first. Carbon or reverse osmosis, used only if the test shows a need, targets dissolved chemicals. UV light or chlorine disinfects, targeting germs. A second checkpoint retests the water before it reaches the tap. Notes say that the steps and their order come from your test results and a professional, and that water softeners swap hardness minerals but do not make water safe to drink.

WaterBudgetOutcomes

The three usual results of a water budget. The middle one, a seasonal gap, is the most common: enough rain over the year, but not when you need it.

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Three small charts, each with monthly bars for the water a roof catches and a line for household use, which is steady most of the year and rises in summer for the garden. The values are illustrative. First, surplus all year: the bars are above the use line every month, so a modest tank may be enough. Second, a seasonal gap: the bars are tall in winter and very short in summer, and the summer months fall below the use line, shaded as shortfall; over the year there is enough rain, so a bigger tank can carry the wet-season surplus forward. Third, a yearly shortfall: the bars are below the use line in every month, so the household needs more roof, less use or another source.

WaterSourcesSection

Five sources in one section. A spring and a well both tap groundwater; a stream, a roof and a town main bring water in other ways.

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A conceptual cross-section of a homestead, not to scale. On the left, a hill rises. Underground, the water table slopes down from under the hill. Below it, groundwater fills the gaps in soil and rock, called the aquifer, and solid rock lies deeper still. Where the water table meets the hillside, a spring comes out on its own and runs down to a stream at the foot of the hill, which is surface water. In the middle, rain falls on a house roof and runs into a storage tank beside the house. To the right, a well reaches down from the surface into the groundwater. At the far right, a municipal water main runs under a road, available only where public pipes reach.

WhoTestsWater

Who checks the water. A public system must treat and test it for you; with a private source, no one tests it unless you do.

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Two rows compared. Top row, a public water system, which is regulated: water goes from the town or utility, is treated and tested by the utility as the law requires, and reaches your tap, with results reported to you each year. Bottom row, a private supply, which is your responsibility: water goes from your own well, spring or rain system, is tested only if you do it, at least once a year with a state-certified lab, and reaches your tap. A note on the tap says that water looking fine is not proof that it is safe.