The Complete Wood Boiler Installation Guide for Swimming Pools

Can you install a wood boiler to act as a swimming pool heater?

The answer is "yes," but you need to know how to heat a pool with a wood boiler, which is best done using a heat exchanger. Because boiler and pool water must remain separate during heat transfer, a heat exchanger is essential in these situations.

In this guide, we'll cover everything you need to know about wood boilers for swimming pool use, from parts and setup to plumbing, water chemistry, and installation troubleshooting.

How a Wood Boiler Heats a Swimming Pool

Boilers heat water in a closed loop system. As part of the loop, the boiler water travels through the insulated PEX lines to the pool equipment, where it then passes through the heat exchanger. At this point, heat is transferred without mixing the pool and boiler water sources. The loop is closed when the warmed pool water returns to the pool through the plumbing circulation system.

What You Need for a Wood Boiler Pool Installation

Here's an overview of what you need for wood boiler pool installation:

Outdoor Wood Boiler or Existing Boiler System

The first thing you need for a wood boiler pool installation is the boiler itself. This acts as the heat source.

Wood boilers represent an ideal heat source due to their high efficiency, reduced reliance on fossil fuels, and cost-effectiveness.

Insulated PEX Piping

PEX piping is necessary to serve as the supply and return lines between the boiler and the pool setup. Proper insulation helps reduce heat loss and increases efficiency.

Pool Heat Exchanger

Having a proper swimming pool heat exchanger is important for keeping boiler water separate from pool water. Tube-and-Shell heat exchangers are the preferred option for most pool applications, as they're best suited to handle higher flow rates.

Circulation Pump

A circulation pump is also a necessity in a wood boiler and pool setup, notably for moving boiler water to and from the heat exchanger. Pump sizing should match the distance, flow requirements, and system layout.

Valves, Fittings, and Controls

Valves, fittings, and controls are key hardware components that make the system easy to control, service, and troubleshoot.

Choose the Right Heat Exchanger for Your Pool

Do you know the best pool heat exchanger for outdoor wood boiler use? Here's a look at the criteria for choosing the right type for your pool:

Stainless Steel Heat Exchangers for Chlorinated Pools

Stainless steel heat exchangers are ideal for chlorinated pool systems because they balance high temperatures and pressure and resist corrosion. Still, chlorine levels must be managed properly to adequately protect the heat exchanger and other equipment.

Titanium Heat Exchangers for Saltwater Pools

Saltwater pools benefit most from titanium or cupro-nickel heat exchangers, as both offer greater corrosion resistance than many other materials. This is especially important because saltwater can be more corrosive than traditionally chlorinated water. Titanium heat exchangers can also be used in chlorinated pools for those seeking a durable, corrosion-resistant option.

Why Plate Heat Exchangers Are Not Always Best for Pools

As noted, tube-and-shell heat exchangers are preferred over plate heat exchangers for pools because they offer larger ports and handle higher flow rates. While plate heat exchangers are more affordable, they have smaller ports that can restrict flow and may be more prone to clogging in pools.

7-Step Wood Boiler Pool Installation

Step 1: Plan the Boiler to Pool Layout

Identify where your boiler is installed relative to your pool, and plan the route for the underground PEX lines. Aside from PEX line distance, you also need to consider service access and where the heat exchanger will need to be installed.

Step 2: Run Supply and Return Lines

Run two insulated PEX lines (one supply line and one return line) between the boiler and pool area. Be sure to clearly label each line and keep them protected underground to prevent heat loss and damage.

Step 3: Install the Heat Exchanger After the Pool Filter

Next, install the heat exchanger after the pool filter so water enters the exchanger. This helps reduce debris buildup inside the exchanger. Be sure to keep the installation easily accessible for cleaning and service.

Step 4: Connect the Boiler Loop to the Heat Exchanger

Now it's time to create the loop. Connect the boiler supply and return lines to the heat exchanger, ensuring proper flow to ensure optimal transfer and to prevent the heat exchanger from failing. Add valves or unions at points throughout the system to allow for service access.

Step 5: Connect the Pool Loop to the Heat Exchanger

Finish the loop by connecting the pool water side of the heat exchanger to the pool plumbing. As pool water enters the exchanger and picks up heat, it should return to the pool. Remember, boiler water and pool water should never mix.

Step 6: Add Controls and Temperature Monitoring

Incorporate an aquastat, thermostat, or other temperature-control setup to help ensure the pool consistently maintains the desired temperature. Proper controls and settings help prevent overheating and inefficient cycling.

Step 7: Test the System Before Regular Use

Once everything is connected, it's time to check the system. Double-check all fittings and other connections for leaks, confirm that water is circulating properly through both the boiler and pool loops, verify the temperature rise, and make any necessary adjustments.

PVC vs. CPVC for Pool Boiler Installations

Most pool plumbing is PVC, but in higher-temperature areas, CPVC may be required. To determine what's best for your setup, check temperature limits and local building codes, and consult the manufacturer before purchasing plumbing materials. It's important not to subject standard PVC plumbing to temperatures above its rating.

Chlorine vs. Saltwater Pool

Chlorinated Pool Systems

Chlorine pool systems are common, but require frequent maintenance to keep chlorine levels within the proper range. Poor water balance can shorten the lifespan of metal components in your installation.

Saltwater Pool Systems

Saltwater systems are more corrosive than chlorine water pools. As a result, titanium heat exchangers are essential for preventing corrosion. Water chemistry in saltwater pools should also be monitored regularly.

Watch Out for These Installation Issues

These types of projects can be prone to various installation issues. Some of the key ones you want to be sure to watch out for include:

• Using the wrong type of heat exchanger material for the pool type.
• Install the heat exchanger before the filter.
• Using undersized or poorly insulated PEX lines.
• Installing a pump without considering distance or flow needs.
• Failing to install valves, unions, or bypasses that make maintenance convenient.
• Using plumbing materials not rated for the system temperature.
• Allowing chlorine or salt levels to get out of range.

Maintenance Tips After Installation

Some tips and best practices to get the most out of your wood boiler heating system include:

• Checking the heat exchanger periodically for buildup or flow restrictions.
• Monitoring pool chemistry to protect the exchanger and plumbing.
• Inspecting visible fittings, valves, and connections for leaks.
• Confirming the circulation pump is operating properly.
• Flushing or servicing the system as needed based on usage and water conditions.

FAQ

Can You Heat a Swimming Pool With a Wood Boiler?

Yes, this is a cost-effective method for adequately heating a pool.

What Type of Heat Exchanger Is Best for a Pool?

A shell-and-tube heat exchanger tends to be the preferred heat exchanger for swimming pool use.

Where Should the Heat Exchanger Be Installed in Pool Plumbing?

The heat exchanger is best installed after the filter but before any chlorinators or chemical feeders to prevent chlorine from corroding the unit's coils.

Can Boiler Water Go Directly Into the Pool?

If you have a wood boiler pool heater, know that the water cannot go directly into the pool. Instead, you should use a heat exchanger to transfer heat without boiler water mixing with pool water.