How To Heat A Swimming Pool with a Wood Boiler

From solar covers to gas heaters to heat pumps, there are numerous ways property owners can effectively heat their pool to create a more comfortable environment for swimming and other uses. Another effective way to heat pool water is to use a wood boiler. In this post, we'll explain how to create a pool heating system with a wood boiler, the benefits of doing so, and other pool heating tips. Read on to learn how you can keep a comfortable pool temperature this season.

How A Wood Boiler Pool Heating System Works

A wood-burning pool heater works by burning wood in an outdoor furnace to heat water, then pumping it through a heat exchanger to warm the pool water via a network of piping. Essentially, cool pool water enters the heat exchanger, is warmed by the hot boiler water, and then returns to the pool, raising temperatures effectively and efficiently. Pool water and boiler water are kept separate during heat transfer.

This setup tends to be more efficient than direct heating for several reasons. One, wood is generally cheaper than gas or electricity, making it a low-cost heating option. And two, wood boilers can quickly heat large volumes of water quickly.

Why Use A Wood Boiler To Heat Your Pool

Aside from the lower operating costs compared to gas- or electric-heated pools, there are several other reasons to consider a wood boiler for your pool. These include:

• You can effectively do it using the existing outdoor boiler system.
• You can heat multiple applications at once with the wood boiler. In addition to the pool, you can heat your garage, home, and more simultaneously.
• It's an ideal solution for heating pools in rural or off-grid areas.

Perhaps most notably, a wood boiler for the pool can help extend your home swimming season, allowing you to safely enjoy your pool earlier in the spring and later in the fall months.

What You Need For A Wood Boiler Pool Setup

There are various key components that you'll need for your wood boiler pool setup. Here's a closer look:

• Insulated PEX piping: These pipes are designed to transport heat from the boiler to the pool.
• Circulation pump: A pool pump circulates pool water through the heat exchanger.
• Pool heat exchanger: This piece is important for separating boiler water from pool water.
• Valves, fittings, and controls: These components are essential for safe and reliable operation. They help ensure proper flow rates through the heat exchanger, prevent boiler overheating, and protect plumbing from high temperatures.
• Thermostat or aquastat: These parts help your pool maintain a safe, consistent temperature.
  

Choosing The Right Pool Heat Exchanger

What type of heat exchanger is right for your pool and wood boiler setup? It largely depends on the type of pool you're heating. Here's a closer look at your options and when certain heat exchangers make sense:

Shell And Tube vs. Plate Heat Exchangers

Shell and tube heat exchangers tend to be the best for pools because they handle high pool water flow rates, have a low pressure drop, and don't easily clog. Consider a stainless-steel heat exchanger with a conventional pool, or a titanium exchanger with enhanced corrosion resistance if you're heating a saltwater pool.

Plate heat exchangers are an alternative option. While less expensive, they tend to have smaller ports, are more prone to clogging, and have shorter lifespans. While plate exchangers can be used, there is less flow due to the smaller ports. We recommend stainless steel tube and shells for chlorinated pools (however, make sure your chlorine levels are in check) and Cupro-nickel or titanium for salt water pools. Cupro-nickel is great, but titanium is the best.

Cupro-Nickel Heat Exchanger

Cupro-nickel heat exchangers are preferred for saltwater pools due to their durability and corrosion resistance. This heavy-duty material is designed to last longer and is highly resistant to more aggressive chemistry.

Sizing Your Heat Exchanger Correctly

It's imperative to match the heat exchanger BTU to your wood boiler's output to ensure efficient heating. For example, an oversized exchanger can lead to a rapid temperature drop. A general rule of thumb is to use 100,000 BTUs for every 10,000-15,000 gallons of pool water. Small pools generally require a 50,000 to 100,000 BTU exchanger, average-sized pools a 150,000 to 250,000 BTU exchanger, and large pools a 300,000 BTU or greater exchanger. If you need assistance with finding the right size heat exchanger, give us a call.

How To Hook Up A Wood Boiler To A Pool

Here's a step-by-step overview of how to install a wood boiler in your pool:

1. Start by running supply and return water lines from the boiler
2. Install the heat exchanger after the filter
3. Connect the boiler loop and the pool loop to the heat exchanger
4. Install pump and flow controls
5. Add temperature control
6. Check the temperature with the thermostat or aquastat

Best System Configuration For Efficiency

One of the key advantages of using a wood boiler to heat your pool is enhanced efficiency compared to alternative heating methods. To ensure you're maximizing efficiency, follow these tips:

• A counterblow heat exchanger ensures wood burns hot and maximizes heat transfer 
• The best PEX lines are high-density and foam-insulated to prevent heat loss during transport, reduce short cycling, and ensure efficient combustion

Common Mistakes To Avoid

As you configure the system, be wary of making mistakes. Some of the common ones to avoid include:

• Using the wrong type or size of heat exchanger
• Installing the heat exchanger in the wrong location
• Incorrect flow direction
• Failing to insulate underground lines
• Using undersized components
• Not including isolation valves for maintenance

How Efficient Is Heating A Pool With A Wood Boiler

As we noted in the opening, heating your pool with a wood boiler represents a more efficient option than conventional methods.

More specifically, wood-fired heat is much cheaper to generate than gas- or electric-fired heat, potentially saving pool owners thousands of dollars per year and tens of thousands over the lifetime of your pool. Additionally, you're using a readily available fuel source (wood) that can be responsibly grown and harvested. Efficiency is even higher in newer boilers, which can reach up to 90%.

What's more, wood boilers can heat your home, garage, and other spaces at the same time they heat your pool.

Pool Heating Setup FAQs

Can you use a wood boiler to heat a saltwater pool?

Yes, but while possible, doing so often requires a titanium or cupro-nickel heat exchanger to prevent saltwater from corroding the system.

What size heat exchanger do I need for my pool?

This depends on your pool size and volume, as well as the desired heating performance. A general rule of thumb is to use 100,000 BTUs for every 10,000-15,000 gallons of pool water. For more information, give us a call or refer to our catalog.

Can a wood boiler overheat a pool?

Yes, overheating is possible, underscoring the importance of carefully managing water flow and heat transfer.

Do I have to reset the digital aquastat every time I power the pool filter on and off?

A properly installed digital aquastat should retain its settings when power is restored. If you're frequently having to reset it, the device may be faulty and require replacement.

Enjoy Your Heated Pool This Summer

For more information on the efficiency and cost savings of using wood boilers as pool heaters, and for information on how to properly configure your boiler to heat your pool's water, contact ALT Heat today. As a leader in alternative heating supplies and components, we're committed to helping you find the right parts for your next project.