Emergency Plumbing

When a water main breaks, a pipe freezes, or a boil-water notice arrives, knowing where your shutoff valves are and how to use them is the difference between a manageable inconvenience and thousands of dollars in water damage. Most homeowners have never traced their water system from street to fixture. This page is the walkthrough you should do before an emergency, not during one.

Your Water System — The Three Shutoffs

Every residential water system has three layers of shutoff control. Know where all three are before you need them.

1. Curb Stop (Street Shutoff)

The curb stop is a shutoff valve in the sidewalk or lawn between the street water main and your house, usually inside a cast iron or plastic utility box flush with the ground (look for a round or rectangular cover stamped "WATER"). The valve requires a curb key (also called a T-bar tool or curb stop key) to operate — a long-handle tool that reaches down to the valve stem. Inexpensive and available at hardware stores or plumbing supply houses.

The curb stop is the authoritative shutoff for the entire property. In a plumbing emergency that cannot be controlled by interior valves, this is the final stop. Turning it fully clockwise closes the water supply. If you cannot locate your curb stop, check your property survey, ask your water utility, or look at the plumbing system map in your home inspection report.

Curb Stop and Utility Authority

In most jurisdictions, the curb stop is owned by the water utility, not the homeowner. Using it for routine control is acceptable in emergencies, but tampering with the meter or installing unauthorized plumbing downstream of the curb stop may violate local codes. Know your utility's policy.

2. Main House Shutoff

Inside the house — typically in the basement, crawlspace, garage, or utility closet — is a main shutoff valve that controls all water entering the home from the utility line. This is your primary emergency valve. It should be a gate valve (round wheel handle) or a ball valve (lever handle). Ball valves are faster: a 1/4 turn closes them. Gate valves require multiple full rotations.

Do this now: Find your main house shutoff and turn it off and back on. Old gate valves can corrode open and fail to close when you actually need them. Testing under non-emergency conditions reveals this before it matters. If the valve does not fully stop water flow, replace it — an affordable repair that a plumber can complete in an hour or two.

Write its location on a card and attach it to your water heater, electrical panel, or somewhere accessible to guests and family members who might need to find it in your absence.

3. Fixture Shutoffs

Every toilet, sink, dishwasher, washing machine, and water heater has its own shutoff valve directly behind or beneath it. Sinks and toilets have oval-handle valves behind the fixture; appliances typically have ball valves on the supply lines.

Walk through your home and locate every fixture shutoff. These allow you to isolate a single leaking fixture without killing water to the rest of the house. Test each one annually — they corrode and fail in place if never exercised.

Draining Pipes to Prevent Freeze Damage

Water expands approximately 9% when it freezes. In a closed pipe, that expansion generates 2,000–5,000 PSI (13,800–34,500 kPa) of pressure — enough to split copper and burst PVC regardless of schedule rating. Draining pipes before a hard freeze costs $0 and 30 minutes. Pipe replacement after freeze bursting costs $500–$5,000+.

The drain sequence follows a simple principle: air in at the top, water out at the bottom.

Procedure — Draining Interior Pipes Before a Freeze

  1. Shut the main house shutoff valve.
  2. Open the highest faucet in the house (usually an upstairs bathroom faucet). Leave it open — this creates an air inlet that allows water to drain down rather than creating a vacuum lock.
  3. Open all other faucets, tub drains, and shower valves from top floor to ground floor, working downward.
  4. Flush all toilets. This empties the tank and bowl supply lines. Pour about 1 cup (237 mL) of plumbing antifreeze (RV-safe propylene glycol, inexpensive at hardware stores) into each toilet bowl and trap to prevent residual water from freezing. Do not use automotive antifreeze — it is toxic and will contaminate your drain system.
  5. Run the lowest-point faucets last (basement utility sink, outdoor hose bibbs). These drain the remaining water from the supply lines.
  6. Drain the hot water heater if the home will be unoccupied for more than a week (see below).
  7. Insulate any exposed pipes in unheated spaces (garage, crawlspace, exterior walls) with foam pipe insulation (inexpensive per linear foot at any hardware store).

Field Note

Many homes have a low-point drain valve on the main supply line — a small hose-bibb or petcock near the lowest point of the plumbing system, often in the basement or near the water meter. Opening this while the main is shut drains the entire supply line in 2–3 minutes. Know if your home has one before you need it.

Water Heater as Emergency Storage

Your water heater is the largest single volume of clean, drinkable water in most homes. A standard residential tank holds:

Tank Size Volume
30-gallon (113 L) One adult's 30-day supply at 1 gal/day
40-gallon (151 L) Family of two's 20-day supply
50-gallon (189 L) Family of three's 17-day supply
80-gallon (303 L) Family of four's 20-day supply

The water is pre-heated and pre-treated (same as your tap water), making it immediately potable. The only catch: when municipal water pressure drops, the tank may partially fill with air as water is drawn out without replacement. To access it:

Procedure — Draining the Water Heater for Emergency Use

  1. Shut off the energy supply to the water heater — gas valve to "pilot" setting, or circuit breaker off for electric models. Running a heating element or gas burner in a tank with low water causes the element to burn out or the thermocouple to trip.
  2. Shut the cold water inlet valve on the supply line entering the top of the heater.
  3. Open a hot water faucet somewhere in the house to provide air relief and prevent vacuum lock.
  4. Connect a garden hose to the drain valve at the bottom of the tank (standard hose thread).
  5. Open the drain valve — water will flow through the hose. Direct it to a clean bucket, not to a drain.
  6. Sediment note: Tanks that have not been drained in years accumulate rust sediment and mineral scale at the bottom. The first few gallons from an unserviced tank may be discolored and should be treated — run through a filter before drinking if the water appears rusty or contains particles. Tanks serviced annually (drain, flush, refill) produce clear water.

A correctly functioning standard tank thermostat maintains water at 120–140°F (49–60°C), which kills most pathogens on contact. Once the water cools in containers, it is stored potable water.

Annual maintenance draining: Flush 2–3 gallons (7.6–11.4 L) from the tank every year to remove sediment. This keeps the tank ready as emergency water and extends heater life.

Toilet Tank Water

The toilet tank (the rectangular reservoir behind the bowl, not the bowl itself) contains approximately 1.6–2 gallons (6–7.6 L) of fresh tap water. Unlike the bowl, this water has not been in contact with waste. It is safe to drink if no tank tablet or chemical drop-in cleaner has been used. Blue, green, or scented chemical tablets dissolve bleach, dyes, and surfactants into the tank water — that water is not safe to drink untreated.

A household with two bathrooms has 3–4 gallons (11–15 L) of accessible emergency water in the toilet tanks, assuming no chemical treatment. This is not a primary storage source, but it is real water you already have.

Pipe Repair — Field Fixes

During a crisis, infrastructure failures may cause pipe breaks inside your home. Temporary field repairs:

Slip-on repair clamps (inexpensive): A rubber sleeve with a metal band that clamps over a cracked pipe section. Handles up to 60 PSI (414 kPa). Good for copper and PVC. Available at hardware stores in standard pipe diameters (1/2 inch / 1.27 cm, 3/4 inch / 1.91 cm, 1 inch / 2.54 cm).

Self-fusing silicone tape (inexpensive): Wraps around a leak and bonds to itself without adhesive. Works on irregularly shaped fittings and threaded joints where a clamp cannot seat. Not a permanent solution — plan to properly repair within 30–60 days.

Epoxy pipe repair putty (inexpensive): Two-part compound that hardens to a watertight seal around cracks and small holes. Works on copper, galvanized, and PVC. Must be applied to a dry surface — shut the main and drain the section before applying.

Swimming Pool Water Considerations

A 10,000-gallon (37,854 L) swimming pool is a substantial water reserve but requires important caveats:

  • Not potable without treatment: Pool water contains chlorine at 1–3 ppm (safe), but also stabilizers (cyanuric acid, 30–100 ppm), algaecides, and pH adjusters. For drinking, filter through activated carbon (Filtration) to reduce chemical load, then treat.
  • Evaporation: An uncovered pool in summer loses 1–1.5 inches (2.5–3.8 cm) per week — 300–500 gallons (1,136–1,893 L) weekly for a standard pool.
  • Sanitation priority: During a grid-down event, consider reducing chemical additions and using pool water for irrigation and sanitation first, conserving stored drinking water for consumption.

Emergency Plumbing Supply Cache

Keep these items accessible — not buried in the back of a storage unit:

  • Curb key / T-bar tool (inexpensive)
  • Channel-lock pliers, 10-inch (25 cm) and 12-inch (30 cm) (inexpensive each)
  • Slip-on repair clamps in 1/2-inch and 3/4-inch sizes (inexpensive each)
  • Self-fusing silicone tape, 2 rolls (inexpensive each)
  • Teflon thread tape, 2 rolls (inexpensive)
  • Propylene glycol plumbing antifreeze, 1 gallon (3.8 L) (inexpensive)
  • Hose and drain bucket (5 gal / 19 L) for water heater access

Cross-References