Chicago Plumbworks covers water heater repair and replacement across Chicago, from gas and electric tanks in bungalow basements to tankless units on garden-unit walls. Where the water is coming from and how old the tank is decide most of what happens next, so start there. If the tank is pouring water onto the floor right now, treat it as an emergency that can’t wait and close the cold valve on top before anything else.
Leaking from the bottom vs the top
Short answer
Water at the top of a water heater usually comes from a fitting, such as a pipe connection, the relief valve or the anode port. Those can be repaired. Water at the bottom can be the drain valve, the relief valve’s pipe or condensation. Water seeping from the tank body means the tank has failed and needs replacing.
A.O. Smith’s installation manual says many water heaters reported as leaking aren’t leaking tanks, and it warns against replacing one until every possible source has been checked. With a water heater leaking, dry the floor and the outside of the tank first, then watch where the water comes back.
| Where the water is | What it usually is | What happens next |
|---|---|---|
| On top, at the pipe connections | A loose or corroded fitting, or condensation on cold pipes in humid weather | The fitting gets resealed or replaced, and the tank stays |
| On top, at a cap between the pipes | The anode rod fitting | Resealed, with the anode checked while it’s out |
| Running down the pipe on the side | The relief valve opening from thermal expansion or high water pressure, or leaking where it threads in | Pressure gets checked, then an expansion tank or a new valve |
| Bottom, at the drain valve | The valve left slightly open, or leaking where it threads into the tank | A new drain valve |
| Under the burner on a gas tank, with a sizzle | Condensation, common after startup and when the incoming water is cold | It should stop once the tank heats up, and gets a second look if it doesn’t |
| Bottom, from the tank body or a seam | The tank has rusted through | Replacement |
Condensation is easy to mistake for a leak in a Chicago winter. The manual explains that exhaust from the burner condenses on the cold tank and drips onto the flame, that it’s worst in winter and early spring when incoming water is coldest, and that it should clear an hour or two after the tank warms up. Water that’s still there the next morning is something else.
The relief valve pipe should end no more than six inches above a floor drain, and it must never be capped or plugged. Chicago’s permit terms also don’t allow its outlet to be piped straight into the drain system. A valve that keeps letting water out is telling you something about the pressure in the tank, so plugging it only hides the warning.
If the water is coming from a pipe above the tank rather than the tank itself, that’s a water line split near the tank, and the heater may be fine.
Water spreading from the tank right now
- Close the valve on the cold supply line at the top of the tank.
- On a gas tank, turn the control knob to off. On an electric tank, switch off its breaker, but only if you can get to the panel with dry feet.
- Stay clear of the relief valve pipe. Anything coming out of it is scalding.
Then call and say whether the water is coming from the tank or from a pipe.
No hot water: the usual causes
Start with gas or electric. They fail in different places, and the label on the tank tells you which one you have.
Gas tanks
A standard gas tank lights its burner from a small pilot flame, and a thermocouple keeps the gas valve open only while that pilot is burning. When the thermocouple fails, the pilot goes out the moment you let go of the knob. Drafts can blow a pilot out too. A heater boxed in by storage or squeezed into a tight closet can also run short of the air it needs to burn. If there’s any smell of gas, don’t try to relight anything. Leave the building first.
Power-vent tanks add a fan and an electronic control. They stop when the power goes out, and the control can lock the burner out and flash a code until the fault behind it is fixed.
Electric tanks
An electric tank heats with elements switched by thermostats behind the access panels, plus a high-limit switch that cuts the power if the water gets too hot. A tripped breaker is the first thing to rule out. If the high-limit keeps tripping, Rheem’s guidance is that something else is wrong, and finding it means testing the thermostats and elements rather than resetting the switch again.
Hot water that runs out too soon
When the hot water starts strong and fades fast, A.O. Smith’s troubleshooting list points to a thermostat set too low, a broken dip tube letting cold water into the top of the tank, sediment, a tank too small for the household, or hot pipes running through an outside wall. Chicago’s hard lake water leaves sediment in the bottom of a tank year after year, and in winter the tank starts from much colder water, so it runs out sooner.
Repair or replace?
A leak from the tank body means water heater replacement, because a tank can’t be patched. For everything else, weigh the age of the tank, the part that failed and the setup around it.
Age. Your plumber can date the tank from the model and serial number on its label, and the FAQ below has the life range to compare it against. Spending on a major part for a tank near the end of that range often makes less sense than replacing it.
The part. Thermocouples, drain valves, relief valves, elements and thermostats are all replaceable on a sound tank. So is the anode rod, a metal rod inside the tank that corrodes so the steel doesn’t. The Department of Energy suggests inspecting it every three or four years. If it’s been eaten down to the core wire, a new one protects a tank that’s otherwise in good shape.
The setup. A.O. Smith’s manual says thermal expansion in a closed water system can cause early tank failure. If the old tank’s relief valve dripped for years and there’s no expansion tank on the line, a new heater faces the same pressure unless one gets added.
Tankless in a Chicago basement
A tankless heater makes hot water as it flows instead of storing it. The Department of Energy puts most units at 2 to 5 gallons a minute, with gas models delivering more than electric. It also says most last more than 20 years, and that a shower plus a dishwasher at the same time can stretch even a large gas unit to its limit.
Chicago’s winter is the sizing problem. In early February 2024 the City measured the water in its mains at about 45°F, and in early August at about 70 to 75°F. Heating that water to 120°F, a common factory setting, takes a rise of about 75 degrees in winter and only about 50 in summer. The same unit puts out fewer hot gallons a minute in February, so a tankless heater that keeps up with two showers in August can run out of hot water in the coldest months.
Then there’s the gas line. One maker’s largest residential condensing unit burns up to 199,000 Btu an hour, against roughly 40,000 to 45,000 for a typical 40-gallon tank. The line that fed the old tank may be too small, and it gets sized for the whole house load following the National Fuel Gas Code.
A condensing tankless unit vents through the side wall with 2-inch plastic pipe or a concentric vent, so it doesn’t need the chimney. It does need a drain for its condensate, through a line at least half an inch across, and a neutralizer where local code calls for one. With no floor drain nearby, a small condensate pump does the job. It needs a 120-volt outlet too, so when the power goes out, so does the hot water. Scale is the last piece: the same manual sets a hardness limit of 200 mg/L and calls for water treatment or more frequent flushing where scale builds up. Chicago’s water comes in under that limit, but it still counts as hard.
Gas, venting and permits
An older gas tank vents through a metal flue pipe, often into a masonry chimney it shares with the furnace. Swap that furnace for a high-efficiency model that vents out the side wall, and the water heater can end up alone on a chimney sized for both appliances. Gas utility safety guidance calls that an orphaned water heater and flags it as a carbon monoxide risk. Have the venting checked whenever either appliance is replaced.
Chicago’s permit terms spell out what a proper water heater install looks like:
- A full-port 3/4-inch shutoff valve on the cold water line, and no valve on the hot side.
- Unions at the connections, with dielectric fittings where copper meets steel.
- A gas shutoff ahead of the connector on a gas heater, plus enough combustion air and clearance from anything that burns.
- A check that any flue pipe being reused is in good condition.
- A working carbon monoxide detector in the unit when the heater burns gas.
A same-type swap (the same type, size and shape of heater) in a residential building up to four stories doesn’t need a building permit, though the work still has to meet the Chicago Construction Codes. Change the type, such as going from a tank to tankless with a new vent through the wall, and it’s no longer an in-kind replacement, so it goes through the City’s permit process.
Wet floor, but the tank checks out?
If the water is pooling because the floor drain next to the heater won’t take it, the drain is the problem, not the tank. Water rising out of that drain during a storm is a separate problem, and water coming up into the basement has its own causes and fixes.