Water Heater Leaking From Bottom: Repair or Replace 2026

Who this is for: Homeowners who just discovered water pooling under their water heater and need to know — in the next 30 minutes — whether to call a plumber, shut down the system themselves, or start shopping for a replacement tonight.

Water leaking from the bottom of a tank water heater almost always means the inner steel tank has corroded through, and the unit needs to be replaced — not repaired. Top leaks (around fittings, valves, or the cold-water inlet) are often repairable for $150–$500, but bottom leaks are tank failures, and tank failures are terminal. The expected cost in 2026 is $1,400–$3,800 installed for a like-for-like replacement, or $3,500–$7,200 to switch to a tankless system. Move fast — a slow leak today becomes a flooded basement within 24–72 hours.

Standard tank water heaters are made of glass-lined steel with a sacrificial anode rod inside. The anode is engineered to corrode first, protecting the tank wall. Once the anode is consumed (typically 6–12 years depending on water hardness and use), the tank itself starts to corrode from the inside out. By the time water appears at the bottom, the tank wall has been eaten through. There is no reliable patch, weld, or sealant that fixes a corroded tank — the failure is structural, the unit is under thermal and water pressure constantly, and any "repair" buys days, not years.