Service
Tankless Water Heater Replacement
Replacing an existing tankless unit that has failed or been outgrown, reusing the gas, venting and condensate work already in place where it is suitable.
- Licensed and insured
- Price agreed before work
- A plumber who works your area
The expensive work is usually already done
This is the main thing that separates a tankless replacement from a first tankless installation.
On a first install, the cost sits in the gas line upsizing, the venting and the condensate arrangement rather than in the appliance. On a replacement, all three are frequently already in place and suitable.
That makes replacing an existing tankless unit substantially cheaper than the original job was. Each element still has to be checked rather than assumed, because venting requirements differ between models and a line sized for an older unit may not suit a larger one.
Find out why it failed first
Replacing the unit without understanding the failure often just resets the clock.
The most common cause of premature failure in hard water is a heat exchanger that scaled up because it was never descaled. That is not a defect in the product, it is the one maintenance item these units genuinely need, and it is the one most owners are never told about at handover.
If that is what happened, the new unit needs a descaling interval matched to your actual water hardness, and someone needs to actually do it. Otherwise the same failure is simply scheduled for a few years’ time.
Does this sound familiar?
Problems this service solves
- A tankless unit with a failed heat exchanger
- A heater that has been outgrown by the household
- An older unit where parts are no longer available
- A unit that was undersized when it was first fitted
- Repeated faults on an ageing tankless heater
Signs you need tankless water heater replacement
If more than one of these is true, the problem is usually past the point a plunger or a store-bought cleaner will fix.
- The exchanger has failed or is leaking
- Repair parts are no longer supplied for the model
- The unit has never kept up with demand
- Faults are becoming frequent rather than occasional
What to expect
How the visit works
Establish why it failed
An exchanger that scaled up through lack of descaling will do it again unless the maintenance changes, so the cause matters as much as the replacement.
Reassess the sizing
If the unit was undersized originally, replacing like for like reproduces the problem. Demand is recalculated rather than assumed.
Assess existing infrastructure
Gas line, venting and condensate are often reusable, which makes replacement considerably cheaper than a first installation. Where they are not, you are told why.
Install and commission
The new unit is fitted, commissioned and set, with the descaling interval matched to your actual water hardness.
What's included
What you get on every job, whoever we send.
- Existing gas and venting reused where genuinely suitable
- Sizing revisited rather than repeated
- The cause of the failure addressed, not just the unit
- A descaling interval matched to local water
Questions
Tankless Water Heater Replacement questions
Is replacing a tankless unit cheaper than the first installation?
Usually yes, sometimes considerably. The expensive parts of a first tankless installation are the gas line upsizing, the venting and the condensate arrangement, and those are frequently reusable. If you are fitting a similar unit in the same position, much of that work is already done. It is worth having each element checked rather than assumed, because venting requirements can differ between models.
My exchanger failed. Was that avoidable?
Often, yes. In hard-water areas the most common cause of premature exchanger failure is scale that was never removed, because descaling is the one maintenance item a tankless unit genuinely needs and it is the one most owners are never told about. If that is what happened, replacing the unit without changing the maintenance simply resets the clock on the same failure.
Should I go back to a tank instead?
It depends why you are replacing. If the tankless unit failed through neglected maintenance and the household is happy with endless hot water, another tankless with a proper descaling schedule makes sense. If it never kept up with demand, or if the maintenance is not going to happen, a well-sized tank can genuinely be the better choice. That is worth an honest conversation rather than a default.
Related services
Tankless Water Heater Installation
Installing on-demand water heaters, including the gas line sizing, venting and condensate handling that the unit itself does not come with.
See what this coversTankless Water Heater Repair
Diagnosis and repair of on-demand water heaters, including error codes, scaled heat exchangers, ignition faults and inadequate flow.
See what this coversWater Heater Replacement
Replacing a water heater that has failed or is near the end of its life, including sizing, removal of the old unit and bringing the install up to code.
See what this coversWater Heater Repair
Diagnosis and repair of gas, electric and tankless water heaters, including no-hot-water calls, leaks, pilot problems and sediment flushing.
See what this covers
Get it fixed
Tankless Water Heater Replacement, handled locally
Call with your ZIP code and what you are seeing. We route you to a licensed plumber in your area who does tankless water heater replacement every week.
- Licensed and insured
- Answered 24/7
- Price before work