How to Install an Indirect Water Heater Using Your Existing Boiler
Installing an indirect hot water heater is a smart way to improve your home’s hot water supply—especially if you’re already using a boiler for heating. This setup uses your existing boiler as the heat source, efficiently transferring heat to the water heater through a built-in heat exchanger. For installation or expert guidance, consider contacting a professional Plumber Near Me.
In this detailed guide, we’ll walk you through how to install an indirect water heater on a boiler, based on expert advice from plumbing and heating specialist Richard Trethewey. Whether you’re upgrading your system or doing a new water boiler installation, this step-by-step tutorial will help you get it done right. You May Also Like: Automatic washing machine shut off valve.
Why Choose an Indirect Hot Water Heater?
An indirect water heater relies on your home’s boiler to heat the water. Since the boiler is often more powerful than a standalone water heater, this setup offers:
- Faster hot water recovery times
- Higher energy efficiency
- Longer lifespan compared to tankless systems
- Reduced fuel usage if your boiler is already running for heating
This type of hot water heater is ideal for homes with high hot water demand or where energy efficiency is a top priority.
Project Overview
- Skill Level: Expert (5/5)
- Estimated Cost: $3,000
- Time Required: 5–6 hours
- Main Focus: How to install an indirect water heater on a boiler
Tools & Materials Needed
Before you begin the water boiler installation, gather these tools:
- Hose
- Water pump
- Propane torch
- Pipe cutter
- Pipe wrench & pliers
- Adjustable wrench
- Level
- ½” & 1″ copper piping
- Ball valves, Y-strainers, mixing valve
- Solder, flux, sand cloth
- Pipe dope & plumber’s tape
- Bucket
- Circulator pump
- Electronic relay & temperature sensor
Step-by-Step Guide: How to Install an Indirect Water Heater on a Boiler
1. Turn Off Power and Water Supply
Start by shutting off the boiler’s power switch and turning off the main water supply to the boiler.
2. Drain the Boiler
Connect a hose and water pump to the boiler’s draw-off valve. Direct the water into a utility sink or outdoors to empty the boiler.
3. Position the Indirect Water Heater
Choose a level and sturdy spot for the new hot water heater. Use a level and shims to make sure the base is flat and stable.
4. Tap Into the Boiler
Locate an appropriate place to connect the boiler to the indirect water heater. It’s best to tap just below the boiler’s waterline to avoid sludge buildup.
Dry-fit 1-inch copper pipes from the boiler to the input of the heat exchanger coil on the heater. Be sure to:
- Add a ball valve for shutoff control
- Install a Y-strainer after the valve to act as a flush point
- Use appropriate fittings with pipe dope and plumber’s tape
5. Prepare and Solder Copper Connections
Before soldering:
- Clean all copper pipe ends with sand cloth
- Apply flux to all connection points
Then, use a propane torch and solder to permanently secure the fittings.
6. Set Up the Return Line
Disconnect the boiler’s draw-off valve. This will now serve as the return line from the indirect heater.
Dry-fit new 1-inch copper piping from the output of the heat exchanger coil back into the boiler. This line should include:
- A circulator pump
- A purge valve
- A ball shutoff valve
- Another purge valve
Once dry-fitted, solder these connections.
7. Connect the Cold Water Supply
Cut into the main cold water supply line using a pipe cutter. Be prepared with a bucket to catch excess water.
Run ½-inch copper pipe from the main supply to the bottom inlet of the indirect water heater. Include:
- A tee coupling to split water between the boiler and the new heater
- A shutoff valve going back to the boiler
- A draw-off valve at the cold inlet of the heater
- A connection to the thermostatic mixing valve
Use proper adapters and secure all joints with solder and plumber’s tape.
8. Connect the Hot Water Feed
Cut the existing hot water line that runs from the boiler to your home.
Then, dry-fit and solder new ½-inch copper piping from the top outlet of the indirect water heater. This line should include:
- A relief valve
- A thermostatic mixing valve
- A final connection to your home’s main hot water line
9. Install the Temperature Sensor and Relay
- Attach the temperature sensor to the tank
- Mount the electronic relay on the boiler
- Wire the sensor to the relay, and connect the relay to the circulator pump
10. Turn Everything Back On
Once all connections are soldered and cooled:
- Turn on the main power to the boiler
- Open the water supply valve
- Use purge valves to bleed any air from the system
- Wait for the tank to fill and begin heating the water
You’ll start noticing improved hot water flow and faster recovery times shortly after.
FAQs
What is a hot water heater and how does it work?
A hot water heater warms up water for your home. It stores hot water in a tank and sends it to your taps when needed.
What is an indirect water heater?
An indirect water heater uses your home’s boiler to heat water. It has a tank with a coil inside, where hot water from the boiler flows and heats the stored water.
How long does it take to install an indirect water heater?
Installation usually takes around 5 to 6 hours, depending on your plumbing setup and the plumber’s experience.
Is an indirect water heater energy efficient?
Yes, it is. Since it uses the heat from your boiler, it can save energy—especially if your boiler is already running often for heating.
Can I install an indirect water heater myself?
It’s a complex job and not recommended for beginners. It involves plumbing, pipe cutting, soldering, and electrical work. It’s better to hire a professional plumber.
Final Thoughts: Upgrading to an Indirect Hot Water Heater
Knowing how to install an indirect water heater on a boiler allows homeowners to improve energy efficiency and increase their home’s hot water capacity. Though this is an advanced project, the long-term savings and performance benefits are well worth the effort.
If you’re unsure about handling a full water boiler installation yourself, it’s always a good idea to consult a licensed 24 hours plumbing near me professional for help.
