Tankless Water Heater with your plumbing project

What is tankless water heater?

From the plumbing side, a tankless water heater is less about the box and more about whether your home can feed it. Gas units often need more fuel capacity than the tank they replace, new sealed venting, condensate handling on condensing models, and power for controls. Electric tankless units need serious circuit capacity. Hard water without a treatment plan turns a retrofit into a descaling subscription. Equipment choice detail lives on the water heater guides; this page is the site readiness check.

How tankless water heater actually works

1. 1

   Gas capacity survey on gas models

   Trace pipe size and length back toward the meter and compare to the unit’s BTU demand. Upsizing gas pipe - and sometimes coordinating the meter - is the common cost bomb on retrofits.

   Watch forA tankless price that assumes the existing half-inch branch is fine without measuring. Ask what pipe size they verified.

2. 2

   Venting and combustion air path

   Tankless units use manufacturer-specified sealed vents with length and termination rules. Old B-vent flues are not a free reuse. Shared chimneys may need rework when the tank leaves.

   Watch for“We’ll use the old chimney” without a written vent design. That is how carbon monoxide and failed inspections happen.

3. 3

   Water, condensate, isolation valves and service clearances

   Isolation valves for descaling, a drain path, condensate neutralisation where required, and clearance for service are plumbing details that decide whether the unit is maintainable.

   Watch forA unit jammed into a closet with no service valves. The first descaling will be a demolition mini-project.

4. 4

   Electrical - even on gas

   Gas tankless still needs power for ignition and electronics. Electric tankless is a panel conversation. Coordinate a licensed electrician when load is non-trivial.

   Watch forDiscovery of a service upgrade after the unit is on site. Check the panel at survey.

What does tankless water heater cost?

Plumber-quoted tankless work is unit plus gas, vent, water and electrical coordination. The appliance is often not the largest line. Hard-water treatment and gas upsizing move totals more than finish colour. See the water heater cost guides for equipment bands.

See the full tankless water heater cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →