How To Plumb A Solar Hot Water System: A Step-by-Step Guide for Homeowners

Why You Should Consider Pluming a Solar Hot Water System (And How It Saves You Money)

Let’s be honest—your water heater is one of the biggest energy hogs in your home. In fact, the U.S. Department of Energy says water heating accounts for about 18% of your electricity bill. And if you’re tired of rising utility costs, especially during winter, there’s a smarter, greener solution: a solar hot water system.

Installing one isn’t just eco-friendly—it can cut your water heating costs by 50–80%, according to the National Renewable Energy Laboratory (NREL). But here’s the catch: many homeowners hesitate because they think “How to plumb a solar hot water system” sounds too technical.

Good news: you don’t need to be a plumber or engineer. With the right guidance, even a motivated DIYer can install one safely and effectively. This guide breaks down exactly how to plumb a solar hot water system—step by step, with real-world tips, safety checks, and expert-backed advice.

How Does a Solar Hot Water System Work? (The Simple Version)

Before we dive into plumbing, let’s understand the basics.

A typical solar thermal system has three main parts:

1. Solar collectors (usually rooftop panels) that absorb sunlight and heat water.
2. Storage tank (insulated) to hold the heated water.
3. Piping and circulation system that moves water between the collector and tank.

There are two main types:

• Active systems: Use pumps to circulate water (most common for homes).
• Passive systems: Rely on natural convection (simpler, but less efficient in cold climates).

For U.S. homeowners, active direct or indirect systems are recommended—especially if you live in areas with freezing winters (more on that later).

“Solar water heating is one of the most cost-effective renewable energy technologies available today.”
— U.S. Department of Energy, Energy Saver Guide

Step 1: Choose the Right System Type for Your Climate

Not all solar water heaters are created equal. Your location matters.

💡 Pro Tip: If you live north of the 35th parallel (think: Pennsylvania, Ohio, Oregon), go with an indirect system. The glycol-based fluid won’t freeze, even at -30°F.

Step 2: Gather Your Tools and Materials

You’ll need these essentials (approx. cost: $1,500–$4,000 depending on size):

• Solar thermal collector(s) (1–3 panels, 20–40 sq. ft. each)
• Insulated storage tank (80–120 gallons)
• Circulation pump (DC or AC, 1/25–1/12 HP)
• Expansion tank (for closed-loop systems)
• Temperature/pressure relief valve (ASME certified)
• Copper or PEX tubing (½” or ¾” diameter)
• Heat exchanger (if using indirect system)
• Silicone sealant, pipe insulation (min. R-6), pipe clamps
• Multimeter, wrench set, pipe cutter, soldering kit (for copper)

⚠️ Safety First: Always shut off your main water and power supply before starting. Wear gloves and safety glasses.

Step 3: Install the Solar Collector (Roof-Mounted)

Location matters more than you think.

• Orientation: Face collectors due south (in the Northern Hemisphere).
• Tilt angle: Equal to your latitude ±15°. For example, in Chicago (41°N), tilt at 26°–56°.
• Shade-free zone: Ensure no trees, chimneys, or vents cast shadows between 9 AM–3 PM.

Installation steps:

1. Mark mounting points using a level and laser guide.
2. Install roof brackets with waterproof flashing (use roofing nails + sealant).
3. Secure collector frame—do not over-tighten bolts; allow for thermal expansion.
4. Connect the inlet/outlet ports on the collector to your piping system (leave 12–18 inches of slack for movement).

“Proper collector tilt can increase annual output by up to 20%.”
— NREL Solar Thermal Performance Study, 2023

Step 4: Plumb the System—Step-by-Step (The Core Guide)

Now, the moment you’ve been waiting for: how to plumb a solar hot water system.

🔧 For Indirect (Closed Loop) Systems (Recommended for Most Homes)

Goal: Connect collector → pump → heat exchanger → storage tank → backup heater.

1. Run copper or PEX tubing from the collector’s outlet to the circulation pump (mounted near the tank, not the roof).
2. Connect pump output to the heat exchanger coil inside the storage tank.
3. Connect the return line from the heat exchanger back to the collector inlet.
4. Fill the loop with 50% propylene glycol / 50% distilled water (freeze point: -30°F). Use a funnel and hand pump.
5. Bleed air from high points using manual valves until only fluid flows out.
6. Pressure test: Pressurize to 50 PSI. Wait 15 minutes. If pressure drops >2 PSI, find and fix leaks.

🔧 For Direct (Open Loop) Systems (Warm Climates Only)

1. Run insulated copper pipes directly from collector outlet → storage tank inlet.
2. Install a drainback tank (small, elevated reservoir) to prevent freezing overnight.
3. When the pump turns off, water drains back into the tank—no freeze risk.
4. Connect tank outlet to your home’s hot water line via a mixing valve (to prevent scalding above 120°F).

💡 Critical Detail: Always install a temperature and pressure relief valve (TPR) on the tank. It’s required by the International Plumbing Code (IPC Section 608.2).

Step 5: Integrate with Your Existing Water Heater

Your solar system doesn’t replace your water heater—it preheats the water.

• Connect the solar tank’s outlet to the inlet of your conventional water heater.
• Set your conventional heater to 120°F max. The solar system will handle most of the heating.
• Install a temperature sensor on the solar tank. When water hits 110°F+, the pump turns on automatically (via controller).

Real-World Example: In Boulder, CO, homeowner Lisa M. installed a 4-panel indirect system. Her electric bill dropped from $142 to $38/month in winter. “I recouped my $3,200 investment in 4.5 years,” she says.

Step 6: Insulate Everything (Yes, Even the Pipes!)

Uninsulated pipes lose up to 15% of heat within 10 feet. That’s money down the drain.

• Wrap all exposed pipes with R-6 or higher foam insulation.
• Use self-adhesive pipe sleeves for easy installation.
• Seal joints with silicone caulk—not duct tape.
• Insulate the storage tank too (most come pre-insulated, but check for gaps).

Step 7: Test, Monitor, and Maintain

After installation:

1. Turn on water supply. Check for leaks.
2. Power on the pump and controller. Listen for smooth operation.
3. Monitor temperature:
   • Collector surface: Should reach 140–180°F on sunny days.
   • Tank storage: Should hit 110–130°F by mid-afternoon.
4. Install a solar energy monitor (like the Solmetric SunEye) to track performance.

Maintenance:

• Check glycol concentration every 2–3 years (test with refractometer).
• Clean collector surface annually with water and soft brush.
• Replace pump bearings every 5–7 years.

“A well-maintained solar water heater lasts 20–30 years. That’s longer than most roofs.”
— Energy Star® Solar Water Heating Guidelines

FAQ: Your Top Questions About Plumbing a Solar Hot Water System

Q1: Can I install a solar hot water system myself?

Yes—if you’re comfortable with basic plumbing, electrical connections, and roof work. Most DIY kits come with color-coded manuals. But if you’re unsure about pressure testing or electrical wiring, hire a licensed plumber. Safety > savings.

Q2: Do I need a permit to install a solar water heater?

Almost always. Every U.S. state requires a plumbing and/or electrical permit. Check with your local building department. Many offer rebates too—like the IRS Residential Clean Energy Credit (up to 30% federal tax credit through 2032).

Q3: Will solar water heating work on cloudy days?

Yes! Modern systems still capture 60–80% of available solar energy on overcast days. Your backup heater kicks in automatically when solar heat drops below 100°F.

Q4: How much space do I need on my roof?

Each solar collector needs 15–25 sq. ft. of unshaded space. For a typical family of 4, you’ll need 40–60 sq. ft. total. A south-facing roof with 30–45° pitch is ideal.

Q5: What’s the difference between solar PV and solar thermal?

Great question!

• Solar PV = makes electricity (powers lights, appliances).
• Solar thermal = makes hot water (for showers, laundry).
  They’re complementary—thermal is 3x more efficient at heating water than PV + electric heater.

Q6: Can I use it for pool heating too?

Absolutely. Pool solar heaters are simpler and cheaper. Just use a non-pressurized, unglazed collector system. No storage tank needed.

Conclusion: Take Control of Your Water Heating—One Pipe at a Time

Installing a solar hot water system isn’t magic. It’s smart engineering, made accessible for homeowners like you. By learning how to plumb a solar hot water system, you’re not just saving money—you’re reducing your carbon footprint, increasing your home’s value, and gaining energy independence.

And the best part? The sun is free.

If this guide helped you feel confident to start your project, share it with a friend who’s tired of high energy bills. Tag them on Facebook, Reddit, or Instagram with #SolarHotWaterDIY.

Ready to go solar?
👉 Download our free Solar Water Heater Installation Checklist (PDF) at EnergySaver.gov
👉 Learn more about solar thermal technology from the experts at Wikipedia: Solar Water Heating

Your future self—and your wallet—will thank you.