What a solar water heater needs to work well
Before you pick up a tool, understand what any solar water heating system requires. According to the U.S. Department of Energy’s 2003 consumer guide, the first consideration is the site. A good location has unshaded areas and generally faces south. A professional installer can evaluate your roof, but if the roof does not have enough space you can also install the system on the ground. The amount of sun your site receives, how often temperatures dip below freezing and other factors affect the type of system you choose.
The DOE guide also explains that you need to consider homeowners association rules and neighborhood bylaws, often called codes, covenants and restrictions. Some cities and counties have ordinances or require permits for home improvement construction, including solar system installation. These rules can shape what you are allowed to build and where.
Freezing temperatures are a critical factor. The DOE guide notes that in freeze-prone climates, solar pool heaters are used mainly in summer, and the freeze risk influences system design choices. Any system exposed to freezing weather needs a strategy to prevent ice from cracking pipes, collectors or storage components.
System sizing: what the DOE guide says
The 2003 DOE consumer guide offers sizing guidelines that contractors have used for years. For domestic water heating, contractors usually follow a guideline of about 20 square feet (2 square meters) of collector area for each of the first two family members. For every additional person, add 8 square feet (0.7 square meters) if you live in the Sun Belt area of the United States, or 12 to 14 square feet (1.1 to 1.3 square meters) if you live in the northern United States.
For active systems, the size of the solar storage tank increases with the size of the collector, typically 1.5 gallons per square foot of collector. The guide describes a small 66-gallon system as usually big enough for one to three people, a medium-size 80-gallon system for a three- or four-person household, and a large 120-gallon system for four to six people. These are the DOE’s 2003 reference points, not current universal standards, but they give you a starting framework for thinking about scale.
For swimming pools, the DOE guide states that heating your pool with solar energy requires a collector that is 50% to 100% of the surface area of your pool. A 15-by-30 foot swimming pool in Florida typically requires a collector that equals 100% of the pool’s square footage, translating to 450 square feet of unglazed flat-plate collectors. In northern California, where most pools are used only 6 to 8 months per year, systems are typically sized at 60% to 70% of the pool’s surface area.
Permits, inspections and contractor licensing
The DOE guide is clear: you will probably need to obtain permits from the building department that has jurisdiction in your state, county or city. Plumbing, building and electrical permits may be required, and these permits typically require a final inspection after the system has been installed. Always obtain the necessary approvals from a homeowners association before beginning construction.
Licensing matters too. The DOE guide says that having a valid plumber’s or solar contractor’s license is required in some states for solar thermal system installation. You can confirm licensing by contacting your state contractor licensing board. Local requirements may also include a local contractor’s license. For certain rebates, your contractor may have to demonstrate special knowledge through a solar contractor specialty license, certification by a group such as a state chapter of the Solar Energy Industries Association, or a letter from the solar heating manufacturer stating the installer has the necessary experience and training.
The Solar Rating and Certification Corporation, ICC-SRCC, describes itself as the leading certifier and standard developer for solar heating and cooling products in North America. Its certifications are designed to help manufacturers comply with building code, regulatory and incentive program requirements. Most building codes in the US require compliance with ICC-SRCC solar standards for safety. If you buy components rather than build them, SRCC-certified equipment helps demonstrate code compliance.
Where DIY can make sense
A DIY approach can be a good fit for projects that stay outside the pressurized drinking-water system and away from roof penetrations that demand code-governed waterproofing. Small demonstration projects let you learn how solar thermal collectors work without tying into household plumbing. Our Small Demonstration Projects page explores ideas that keep the stakes low.
DIY pool heating is another area where homeowners often take on more of the work. The DOE guide notes that most people do not need or use a backup heater with solar pool heaters, and in climates where it rarely freezes, pool heaters may be used year-round. Pool systems typically circulate pool water directly through unglazed collectors, which is simpler than heating potable water. See DIY Pool Heaters for how pool collectors and pumps work together.
If your goal is understanding solar thermal principles, building a small batch heater or a thermosiphon loop that sits on the ground and heats water for outdoor use can be a valuable learning experience. Our DIY Solar Water Heater Basics section walks through the core concepts.
When a licensed plumber or contractor is needed
Anything connected to a home’s pressurized drinking-water supply must follow local plumbing and building codes and may require a permit and a licensed plumber. The DOE guide states that plumbing, building and electrical permits may be required, and a final inspection is typically needed. A DIY connection to the house water supply can create risks: backflow contamination, pressure buildup, scalding water and leaks inside walls or ceilings.
Roof penetrations are another boundary. The Florida Solar Energy Center’s 2006 manual, which is Florida-focused, discusses mounting collectors on roofs and emphasizes structural and waterproofing details. If you need to anchor collectors to a roof, a contractor who understands roof load, flashing and local wind-uplift codes can prevent leaks and structural damage. Our Roof and Structural Safety page covers what to weigh before climbing up.
Scalding prevention and pressure relief also belong in the plan. A tempering or mixing valve limits the temperature delivered to taps, and storage tanks use pressure and temperature relief valves; your local code and the equipment manual set the exact requirements. The Scalding Prevention and Pressure and Temperature pages explain these safeguards.
Maintenance: what the sources say you will need to do
The DOE guide addresses maintenance directly. It says that properly maintaining your system will keep it running smoothly, and that regular maintenance on simple systems can be as infrequent as every 3 to 5 years, preferably by a solar contractor. Systems with electrical components usually require a replacement part or two after 10 years.
The guide also describes simple checks you can perform yourself. For example, one easy way to check the system is to carefully feel the hot-water pipes going into the storage tank after the system has been working on a clear, warm day. If the pipes are hot, your system is working properly. Passive systems do not require much maintenance. For active systems, the guide recommends discussing the maintenance requirements with your system provider and consulting the system owner’s manual. Plumbing and other conventional components require the same maintenance as conventional systems.
Glazing may need to be cleaned in dry climates where rainwater does not provide a natural rinse. The DOE guide mentions this as part of the maintenance picture. Our DIY Maintenance and Troubleshooting section covers leak checks, temperature problems, winterizing and water quality issues in more detail.
Checklist: questions to ask before you start
Use these yes-or-no questions to gauge whether a DIY solar water heater fits your situation. Answer honestly; a “no” does not mean solar thermal is out of reach, it often just means you need a contractor for part of the work.
- Does your site have unshaded, south-facing space on the ground or an accessible roof?
- Do you understand your local freeze risk and have a plan to handle it?
- Will the system connect to your home’s pressurized potable water supply?
- Have you checked whether your local building department requires permits and inspections for solar thermal work?
- Are you prepared to install or verify a tempering valve and pressure and temperature relief valve?
- If roof mounting is needed, do you have a plan for structural attachment and waterproof flashing that meets code?
- Can you commit to periodic maintenance, including checking pipes, cleaning glazing in dry climates and replacing electrical parts after roughly 10 years?
- Have you reviewed your homeowners association rules and any local permit rules that may apply?
- Are you choosing components that are certified to ICC-SRCC standards where building codes require it?
For a deeper look at the risks and code boundaries, read Limitations and Risks and Codes and Professional Review. The parent section Is DIY Right for You helps you weigh the full picture.
Frequently asked questions
Can I build a solar water heater entirely on my own without involving a contractor?
You can build a standalone system that does not connect to your home’s pressurized plumbing, such as a small batch heater or a ground-mounted thermosiphon loop used for outdoor washing. The DOE guide and building code realities mean that any connection to the household potable water supply typically requires permits, inspections and licensed plumbing work. Keep any project that is not code-approved completely separate from household plumbing.
Is a DIY solar pool heater easier than a domestic water heating system?
According to the DOE guide, most people do not need a backup heater with solar pool heaters, and the plumbing loop is often simpler because it circulates pool water directly through unglazed collectors. That said, you still need to size the collector correctly, manage pump integration and protect the system from freezing if you live in a cold climate.
Do I really need a backup water heater if I build a solar system?
The DOE guide states that solar water-heating systems almost always require a backup system for cloudy days and times of increased demand. The backup is typically a conventional gas or electric water heater and may already be part of the solar system package. For pool heating, most people do not use a backup heater, though spa owners may use one to reach higher temperatures. A DIY solar water heater that serves a household need will almost certainly need a backup heat source.
Ready to explore the full landscape of DIY solar thermal? Start with our pillar article DIY Solar Water Heater Basics: How They Work and What to Weigh and the category page Is DIY Right for You.
