Repair or replace a water heater
A decision from the leak, the age, and the two quotes, including the failures that are not repairs at all.
Replace a storage tank when the steel shell leaks. Repair it when a control, an element, a thermocouple, or a valve fails and the vessel is young enough that the part is not a donation to a tank you will scrap next year. Between those poles, get two numbers on the same visit: the repair, installed, and the replacement, installed, including pan, expansion tank, permit, and haul-away.
The Department of Energy’s 10-to-15-year band for storage and heat pump heaters, and about 20 years for tankless, is the age context from how long they last. The dollar context is the published ranges in what heaters cost, used only to judge whether the quotes are in a recognizable universe.
A common contractor heuristic says to replace when the repair exceeds about half the cost of a new installed heater and the tank is past the early part of its life. It is a heuristic, not a code. A $400 gas valve on a four-year-old tank is a repair even if someone is eager to sell a heater.
A $400 gas valve on a fourteen-year-old tank with rust in the hot water is a repair only if you want a short extension and you accept the risk of a shell leak. The half-cost idea is a way to force the comparison. It is not a reason to skip the second quote.
Failures that are replacements
Water from the jacket, from a seam, or from a rust hole in the steel is the end. Sealant, clamps, and a tighter fitting do not restore a pressure vessel. Shut the water and the fuel or power, and replace the heater.
The diagnosis steps are is the heater leaking. Do not let a slow drip “wait until after the holidays” if it is the shell and the heater sits over a finished ceiling. The schedule will be chosen for you.
A temperature-and-pressure valve that has been capped is not a repair candidate until the cap is gone and the reason it was capped is fixed.
A flue that spills, a gas valve that will not shut down, or wiring that has scorched are not “keep using it while the part ships” situations. Make the heater safe the same day.
Safe sometimes means off, with no hot water, until the truck arrives. That is an acceptable outcome. Hot water is a comfort. A defeated safety device is not.
A tankless heat exchanger that fails a pressure test or leaks at the coils is a major part or a new unit. If the unit was never descaled and the warranty excludes that neglect, the part price will be yours.
Compare it with a new installed heater that includes service valves. A repeated exchanger failure means the water or the sizing was never addressed. Fixing only the part repeats the invoice.
Failures that are usually repairs
Thermostats, heating elements, thermocouples, igniters, flame sensors, and drain valves on a tank that is not yet old are ordinary repairs. The electric and gas pages describe the symptoms: electric no hot water, gas no hot water, pilot will not stay lit.
Ask the technician to say which part failed and what test showed it. “The control is bad” is weaker than “the thermocouple voltage collapsed with a good flame” or “the element reads to ground.” You are paying for the test as much as for the part.
A dipping relief valve on a young tank is often an expansion tank or a new valve, not a new heater. Diagnose it with why the valve drips so you do not buy a heater to solve a check valve at the meter.
A broken dip tube is a small part that imitates a failed heater. Hot water that runs out covers that pattern. Replace the tube before you replace the tank, unless the tank is already at the end of the DOE band and you were going to replace it anyway.
Repeated element failure is a reason to look at dry fire, sediment, and voltage, not a reason to buy a third element without a question. One grounded element is a repair. An element every year, plus brown water, is a tank that is telling you the anode and the lining are done.
The middle, where quotes matter
A circuit board or a gas valve on a tank between about eight and fifteen years old is the uncomfortable zone. Parts for some older controls are scarce, and a universal replacement is not always listed for the model.
A board that costs as much as a new atmospheric tank, before labor, is a replacement unless the vent and the location make the new install unusually expensive. Write both numbers down. Include the cost of bringing the install up to current code.
A repair that leaves an uncapped relief discharge and a missing pan is cheaper because it is incomplete.
A replacement that adds those items is the correct scope, and it will look more expensive for reasons that are not the heater.
Heat pump repairs split the same way. A fan or a control on a five-year-old unit with a sound tank is a repair. A failed compressor out of warranty, plus a tank that is twelve years old, is usually a replacement.
Get the refrigerant diagnosis before you accept “the whole thing is junk.” Elements may still be heating the water, which disguises the failure and inflates the bill. The heat pump guide explains the modes so you can tell the technician what the display has been doing.
Tankless boards and fans in the middle of that 20-year span are worth repairing when the exchanger is clean and the parts are available. Add the service valves if they were never installed, or the next failure will be scale.
Do not repair a tankless unit that is undersized for the winter rise and also scaled. You would be buying a repaired version of the wrong machine. Size it while the technician is there.
Changing to a tank, if the gas line and the vent were the expensive part of the original tankless job, can be the rational retreat. It can also be a second expensive vent. Price the actual scope.
Checklist: decide from evidence
- Shell leak, spilled flue, scorched wire, or a capped relief valve: replace or make safe today. Not a watch-and-wait.
- Young tank, failed element, thermostat, igniter, or thermocouple, with a test that names the part: repair.
- Drip at the relief pipe with a dry jacket: expansion tank or new valve, not a new heater, unless the tank is already old.
- Short showers with a sudden onset: dip tube or lower element before a new tank.
- Repair price against replacement price, same day, same scope, code items included.
- Past the DOE band, repair only to buy a chosen amount of time.
- Parts no longer listed for the model: replacement, unless a listed substitute exists.
- The water and the vent that caused the failure are corrected on the new install. Otherwise the new relief valve drips or the new exchanger scales.
Timing and emergencies
A planned replacement gets you the model you sized, the vent material the manual requires, and a permit inspection on a normal calendar. An emergency replacement gets you the unit on the truck and a scope decided while the floor is wet.
If the tank is inside the last years of the DOE range, scheduling the replacement is the cheaper way to buy the same machine. If a repair can carry you to that scheduled date, the repair is a bridge, and you should say so. Bridges are legitimate. Bridges that become the plan, year after year, are how a $200 valve is followed by a ceiling repair.
Get the permit question answered before the old tank is disconnected. Some cities inspect the new work only, and some want to see the old vent. The installer who knows the inspector is worth more than the installer who is cheapest because they skip the call. When to call a pro includes the license and permit questions to ask before anyone unbolts the old heater.
Sources
U.S. Department of Energy, Energy Saver, “Which Water Heater Is Right for You?,” for the service-life bands that frame the age half of this decision. Manufacturer parts and warranty documents, for whether a control is still listed and what a tank or heat-exchanger warranty actually covers. HomeAdvisor and ENERGY STAR installed-cost ranges, cited in the cost guide, as the reasonableness check on the replacement number. IRC and local permit practice, via the permits guide, for the scope that belongs in the replacement price.