Remove A Rinnai Unit And Plumb For A Water Heater: The Ultimate Guide

Are you tired of inconsistent water temperatures or high upfront maintenance costs associated with your current tankless system? Many homeowners in the US are finding that a traditional storage tank water heater better suits their household’s specific hot water demands and budget constraints. If you are ready to make the switch, learning how to remove a Rinnai unit and plumb for a water heater is the critical first step toward restoring reliable comfort to your home. This guide will walk you through the process with professional precision, ensuring safety and compliance every step of the way.

Why Switch From Tankless to Traditional Storage?

Before we dive into the tools and wrenches, it is essential to understand why you are making this change. While tankless systems like Rinnai are famous for energy efficiency, they aren’t perfect for every home.

According to industry data, while tankless heaters can be 24%–34% more energy-efficient than conventional storage tank water heaters for households that use 41 gallons or less of hot water daily, larger families often struggle with flow rate limitations. If you have multiple bathrooms running simultaneously, a tankless unit might struggle to keep up, leading to the dreaded “cold water sandwich” effect.

Switching to a traditional tank system offers:

• Consistent Flow Rates: A 50-gallon tank can deliver hot water to multiple fixtures simultaneously without a drop in pressure.
• Lower Upfront Costs: Traditional units are generally significantly cheaper to purchase and install than high-end tankless models.
• Simpler Maintenance: No need for annual descaling or complex electronic board diagnostics.

For a broader understanding of water heating technologies, you can review the general principles of water heating systems on Wikipedia.

Tools and Materials You Will Need

Professional plumbers never start a job without the right gear. To successfully remove a Rinnai unit and plumb for a water heater, gather the following items before turning off a single valve.

Essential Tools

• Pipe Wrenches (2): One for holding, one for turning.
• Tubing Cutter: For clean cuts on copper piping.
• Propane Torch or Sweat Fitting Tool: If soldering copper connections.
• Push-Fit Fittings (SharkBite style): Excellent for DIYers who want to avoid soldering.
• Bucket and Towels: To catch residual water.
• Voltage Tester: Crucial for electrical safety.
• Gas Leak Detector Solution: Soapy water in a spray bottle.

Materials for the New Install

• New Storage Water Heater: Ensure it matches your gas type (Natural Gas or Propane) and fits your space.
• Flexible Gas Connector: Stainless steel, correct diameter and length.
• Dielectric Unions: To prevent corrosion between dissimilar metals (copper and steel).
• Teflon Tape & Pipe Dope: For sealing threaded connections.
• Venting Materials: Type B gas vent pipe if your new unit requires different venting than the Rinnai.

Step-by-Step: How to Remove a Rinnai Unit

Safety is paramount. Working with gas and water carries inherent risks. If you smell gas at any point, stop immediately and call your utility provider.

1. Shut Off Utilities

Locate the gas shut-off valve near the Rinnai unit and turn it to the “Off” position (usually perpendicular to the pipe). Next, turn off the water supply valves located on the inlet and outlet pipes of the unit. Finally, disconnect the electrical power. Even gas tankless units require electricity for the control board and fan. Unplug the unit or flip the dedicated breaker in your panel.

2. Drain the Unit

Open the hot water taps in your house to relieve pressure. Attach a hose to the drain valve or service port on the Rinnai unit and direct it into a bucket or floor drain. Open the valve to let remaining water escape. Note: Tankless units hold very little water compared to tanks, so this step is quick.

3. Disconnect Gas and Water Lines

Using your pipe wrenches, carefully unscrew the flexible gas line. Cap the gas line immediately with a proper metal cap to prevent debris entry and potential leaks. Next, disconnect the hot and cold water lines. If these are soldered, you will need to cut the pipe a few inches away from the unit using a tubing cutter.

4. Remove Venting and Mounting

Unscrew the vent pipe from the top of the Rinnai. Be gentle, as you may reuse some components depending on your new heater’s requirements. Once all connections are free, lift the unit off its mounting bracket. These units can be heavy; having a helper is recommended. Unscrew the bracket from the wall and patch any holes if necessary.

Preparing the Space for a Traditional Water Heater

This is where the job changes significantly. A tankless Rinnai is compact and often wall-mounted outside or in a closet. A traditional water heater is large, cylindrical, and sits on the floor.

Assessing Floor Space and Structural Integrity

A standard 50-gallon water heater weighs over 100 pounds empty and nearly 500 pounds when full. You must ensure the floor can support this load.

• Location: The new unit usually needs to be within 6 feet of the existing gas line and water connections to minimize re-piping.
• Pan and Drain: Most US building codes now require a drain pan under indoor water heaters with a drain line leading to the exterior or a floor drain. This catches leaks before they damage your ceiling or flooring.

Adjusting Plumbing Connections

The inlet and outlet positions on a tank heater are on the top, whereas your Rinnai likely had side or bottom connections configured differently.

• Cold Inlet: Usually on the right (looking from the front).
• Hot Outlet: Usually on the left.
• Extension Pipes: You may need to solder or use push-fit fittings to extend your existing copper lines down to the top of the new tank.

Pro Tip: Use dielectric unions where copper pipes meet the steel nipples of the water heater. Without these, galvanic corrosion will eat through your connections within a few years, leading to catastrophic leaks.

Installation: Plumb and Connect the New Heater

Now that the Rinnai is gone and the space is prepped, it is time to install the new system.

1. Position the Water Heater

Place the drain pan on the floor, then set the water heater inside it. Ensure the unit is perfectly level. An unlevel tank can cause premature wear on the internal anode rod and affect operation.

2. Connect Water Lines

Attach the dielectric unions to the tank’s hot and cold ports. Wrap the threads with Teflon tape and apply pipe dope. Tighten securely. Connect your home’s copper piping to the unions.

• Cold Side: Install a new shut-off valve here if one doesn’t exist.
• Hot Side: Ensure the pipe is clearly marked or color-coded red to prevent confusion later.

3. Connect the Gas Line

Use a new, certified flexible gas connector. Apply pipe dope to the male threads only (never on the flare). Connect one end to the gas pipe in the wall and the other to the water heater’s gas control valve.

• Warning: Do not overtighten, as this can crack the flare fitting. Hand-tight plus a quarter turn with a wrench is usually sufficient.

4. Venting Requirements

Unlike the sealed combustion or direct vent of many Rinnai units, atmospheric gas water heaters rely on natural draft. You must install a Type B double-wall metal vent pipe that rises vertically.

• Ensure there is a minimum 1/4 inch rise per foot of horizontal run (though vertical is preferred).
• The vent must terminate at least 12 inches above the roof line and away from windows.

Testing and Safety Checks

Do not turn on the gas yet. Follow this strict sequence to avoid damaging the new tank.

1. Fill the Tank First

Crucial Step: Open the cold water supply valve to the heater. Then, go inside the house and open a hot water faucet (e.g., a bathroom sink). Let it run until a steady stream of water flows with no sputtering.

• Why? If you turn on the gas burner while the tank is empty, you will instantly ruin the heating elements or crack the glass lining. The tank must be 100% full of water before heat is applied.

2. Check for Leaks

Inspect every connection you made—water and gas. Use your soapy water solution on the gas fittings. If bubbles form, you have a leak. Tighten slightly and re-test.

3. Ignition

Once confirmed full and leak-free, turn the gas control knob to “Pilot.” Follow the manufacturer’s lighting instructions (usually involving pressing a red button while sparking an igniter). Once the pilot is lit, turn the knob to “On.”

4. Temperature Setting

Set the thermostat to 120°F (49°C). This is the recommended temperature by the U.S. Department of Energy to prevent scalding while inhibiting bacterial growth.

FAQ: Common Questions About Removing Rinnai and Installing Tanks

1. Can I reuse the venting from my Rinnai unit for a traditional water heater?

No. Rinnai tankless units often use PVC piping for intake and exhaust (concentric venting) or specialized stainless steel for category III/IV appliances. Traditional atmospheric gas water heaters require Type B metal double-wall venting to handle higher temperatures and rely on natural draft. Reusing PVC is a severe fire and carbon monoxide hazard.

2. Do I need a permit to swap my water heater?

In almost all US jurisdictions, yes. Replacing a water heater involves gas, water, and venting modifications, which require a permit and often a final inspection by your local building department. Skipping this can void your home insurance and create safety liabilities.

3. How long does it take to remove a Rinnai and install a tank?

For a professional plumber, the job typically takes 4 to 6 hours. For a skilled DIYer, plan for a full day (8+ hours), especially if you need to modify gas lines or fabricate new venting.

4. What size water heater should I buy to replace my Rinnai?

This depends on your household size.

• 1–2 People: 30–40 gallons.
• 3–4 People: 40–50 gallons.
• 5+ People: 50–80 gallons or consider two smaller units. If your Rinnai was rated for 9 GPM, a 50-gallon high-recovery tank is usually a suitable equivalent for average family use.

5. Is it difficult to convert the gas line from tankless to tank?

Usually, no. Tankless units often require a larger gas line (3/4 inch or 1 inch) due to high BTU demand. Traditional tanks require less gas volume. Therefore, your existing gas line is likely oversized for the new tank, which is safe and acceptable. You will just need a reducer fitting at the appliance connection.

Conclusion

Making the decision to remove a Rinnai unit and plumb for a water heater is a significant home improvement project that can greatly enhance your daily comfort, especially if your family has outgrown the flow capacity of a tankless system. By following this guide, prioritizing safety, and adhering to local codes, you can ensure a smooth transition to a reliable traditional storage system.

Remember, while DIY is rewarding, gas work carries risks. If you are unsure about venting or gas connections, hiring a licensed professional is always the wisest investment.

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