Quick answer
A like-for-like tank water heater replacement takes two to four hours, and you have hot water again the same afternoon. Switching from a chimney-vented tank to a power-vent unit adds a couple of hours for the new side-wall vent, and converting to tankless is a full day because of gas-line and venting work. Draining the old tank is usually the slowest single step.
How long water heater replacement takes depends far more on what is changing than on the tank itself. Swapping a 40-gallon gas tank for another 40-gallon gas tank in the same spot is a short morning; changing the fuel, the venting or the type of heater turns it into a day. Below is what each version of the job looks like on the clock in a typical Burlington, Oakville or Hamilton house.
A like-for-like tank swap: two to four hours
- First 30 to 45 minutes: shut the gas and water, open a hot tap upstairs, hose the old tank to the floor drain and let it empty. A 150–190 litre tank drains slowly through a small valve, slower still if sediment keeps clogging it.
- Next 30 minutes: disconnect gas, water and vent, walk the old tank up the stairs, and bring the new one down.
- Next hour: set the new tank, remake the water connections with new fittings, reconnect the gas with a fresh drip leg and leak-test it, and reconnect the vent.
- Final 30 minutes: fill and purge air, light and adjust the burner, check the draft, set the temperature and walk you through the controls. Hot water is usable within an hour of lighting.
What stretches the job
- Chimney-vent to power-vent — a new PVC exhaust has to be routed through the rim joist to an outside wall and an outlet added nearby, typically adding two hours. Common in 1970s–90s houses in Glen Abbey and River Oaks where the furnace already left the chimney.
- Tight access — a tank in a finished-basement closet in a 2000s+ Alton Village or Joshua Creek build, or a low crawl-space hatch, means more careful moving and sometimes a shorter, wider tank.
- Wider new tanks — heaters built to the current efficiency regulations carry thicker insulation and are a couple of inches wider than the tank they replace, which occasionally forces a rework of the alcove or piping.
- Corroded shut-off valves — a main valve that will not close means shutting the water at the street, which in Halton means arranging the Region's curb stop.
- Electric to gas or gas to electric — running a new gas line or a new 240-volt circuit is a separate trade visit and can push the job to two days.
Tank to tankless: plan on a full day
A conversion to a wall-hung tankless unit is different work: the gas supply often has to be upsized because tankless draws several times the gas of a tank, new venting and a condensate drain are needed, and the water lines move to the wall. In most houses that is six to eight hours with two technicians. The gas-line upsizing alone can add $400–$1,200 to the quote, which our tankless cost guide covers in detail. Our tankless water heater page walks through what a conversion day involves.
Rental returns add a step, not a day
If the old tank belongs to Enercare or Reliance, it does not go to the scrap yard with us. The rental company has to be notified, the account closed or bought out, and the unit returned or collected. We handle the disconnect and set the old tank aside; our rental buyout service walks you through the paperwork side so there are no surprise charges after the fact.
How soon can it be scheduled?
For a leaking or dead tank we aim for same-day installation. Our shop sits on North Service Road in Burlington, a few minutes off the QEW, which puts most of Oakville, Burlington and Hamilton within a short drive with a tank already on the van. The gas connection is made by a TSSA-licensed technician and the venting is done to the CSA B149.1 gas code, so nothing has to be redone on a return visit. The only true delay is a non-stock size or a specialty unit that has to be ordered.
Cost and timing go together, so read our answer on what a water heater replacement costs in Ontario alongside this one. To get a tank scheduled, contact ZK Mechanical with the size and fuel of your current heater and a photo of the top of the tank, and we will confirm a time and a written price.