Water heaters
Tankless water heater installation and repair
A tankless water heater heats water as it flows instead of storing it, so it does not run out, and it takes up far less space. Installation often needs a larger gas line or electrical circuit and new venting. In hard-water areas the unit must be descaled about once a year.
- Emergency plumbing help
- Licensed local plumbers
- Price confirmed before work
Tankless units are sized by flow rate: how many fixtures can run at once at your incoming water temperature. Cold groundwater in northern states lowers the output of the same unit, so sizing that works in Florida can fall short in Minnesota.
Switching from a tank is a bigger job than replacing like with like. Gas models typically need more gas than the old tank used, plus sealed venting through a wall or roof. The plumber checks the gas meter, line size and vent route before quoting.
Tankless Water Heaters at a glance
- Sized by
- Flow rate and incoming water temperature
- Typical life
- Around 20 years with maintenance
- Maintenance
- Descale yearly in hard-water areas
- Often needed
- Larger gas line, new venting, condensate drain
Updated · How we write our pages
What are the signs you need a plumber?
- An error code on the display
- Hot water that turns cold and hot again mid-shower
- Lower hot water flow than before
- The unit shuts down under heavy demand
- You want to free up floor space or stop running out of hot water
What does the plumber do?
- 1
Assess the home
The plumber checks gas or electrical capacity, vent routes and peak hot water demand.
- 2
Size the unit
Flow rate is matched to the number of fixtures and the local groundwater temperature.
- 3
Install and vent
The unit is mounted, piped with service valves, vented and connected with a permit.
- 4
Commission
Gas pressure and temperature are set, and the descaling routine is explained.
What affects the cost of tankless water heaters?
It depends on the job, and a plumbing company can only give a firm price after seeing it. Prices also vary by region and by time of day. These are the factors that move a quote up or down. Ask for the price in writing before work begins.
- Gas line or electrical upgrades
- Vent length and route
- Unit capacity and whether it is condensing
- Adding a recirculation loop or water treatment
What can you do yourself, and when should you call a plumber?
Safe to try
- Clean the inlet water filter as the manual describes
- Write down any error code before calling
- Descale with a pump kit if you are comfortable with the service valves
Call a plumber when
- Don't alter gas piping or venting
- Don't ignore repeated ignition or flame failure codes
Tankless Water Heaters questions
Is a tankless water heater worth it?
It suits households that run out of hot water, want the floor space back or plan to stay in the home long enough to benefit from the longer service life. The upfront cost is higher than a tank, mostly because of gas, venting or electrical upgrades.
Why does my tankless heater go cold for a moment?
That is often a cold water sandwich: a slug of unheated water between two draws. It can also point to scale on the heat exchanger or a flow rate below the unit's minimum.
How often should a tankless heater be descaled?
About once a year where water is hard, and every couple of years where it is soft. Scale on the heat exchanger reduces output and eventually triggers error codes.
What is a tankless water heater?
A tankless water heater heats water as it flows through a heat exchanger, without storing it. It runs only when a hot tap is open, so it does not run out, but its output is limited by its flow rate.
How long does tankless installation take?
Replacing an existing tankless unit takes a few hours. Converting from a tank usually takes most of a day, because of the gas line, venting and condensate drain.
Can a tankless water heater run during a power outage?
No. Gas tankless units still need electricity for the controls, igniter and fan. A small battery backup can keep one running through a short outage.
Do tankless water heaters work with hard water?
Yes, but scale builds on the heat exchanger faster. In hard-water areas the unit should be descaled yearly, and a softener or scale filter ahead of it protects the warranty with some manufacturers.
Where we connect homeowners with plumbers
Tankless Water Heaters requests are taken from across the United States. Local conditions change the work, so start with your city or find your state.
Related services
Water Heater Replacement
Replacing a leaking or aging water heater? See how plumbers size, install and permit a new tank, and call to reach a local installer..
Learn moreWater Heater Repair
No hot water, lukewarm showers, popping noises or a leak at the tank? See what can be repaired and call to reach a local water heater plumber..
Learn more
Guides on this topic
How long does a water heater last?
Typical lifespans of tank, tankless and heat pump water heaters, how to read a heater's age from its serial number and the signs it is time to replace.
Read the guideTankless vs. tank water heater: which is right for your home?
Compare tankless and tank water heaters on upfront cost, lifespan, hot water supply, maintenance and what installation requires in your home.
Read the guideWater heater not heating: causes and what to check
No hot water or only lukewarm water? Check the breaker, the reset button or the pilot first, then see which parts usually fail on gas and electric heaters.
Read the guide
Need a plumber for this?
Call and tell us what's going on. Calling is free, and the plumber confirms the price before any work starts.