Reliance Water Heater Leaking: Find the Source and Fix It

Common Symptoms

• Water puddle on the floor directly beneath the Reliance water heater
• Drip or stream from the drain valve at the bottom of the tank
• Water discharging from the TPR (temperature-pressure relief) valve discharge pipe
• Dripping from the cold-water inlet or hot-water outlet fittings at the top of the tank
• Weeping or moisture around the anode rod hex port on the top of the tank
• Seeping around the element cover plate on a Reliance electric 12-Series model
• Rust staining on the outside of the tank body (indicating tank body corrosion)
• Water only appears during tank heating cycles (thermal expansion leak from TPR or fittings)

Most Likely Causes

1. 1

   Reliance Drain Valve Drip — Plastic Factory Valve Failure

   Most Reliance residential tank water heaters ship with a factory-installed plastic drain valve (polyethylene body with a hose-thread outlet). These plastic valves are prone to slow drip-leaks from two locations: (1) from the hose-thread outlet cap (the plastic cap is not fully seated or the valve is corroded open slightly) — fix is tightening the cap or installing a brass hose cap; (2) from the threaded joint between the valve body and the tank spud — the plastic-to-steel joint can crack or the valve can loosen over years of thermal cycling. For a drip at the valve cap, cap tightly. For a drip at the body-to-tank joint with the valve fully closed, the plastic valve should be replaced with a ball-type brass drain valve (Watts or equivalent 3/4-inch MPT drain valve). This requires draining the tank fully.

2. 2

   TPR Valve Discharging — Thermal Expansion or Valve Failure

   The temperature-pressure relief (TPR) valve on Reliance water heaters is a safety device that discharges water if pressure exceeds 150 psi or temperature exceeds 210°F. Intermittent dripping from the TPR discharge pipe is usually caused by thermal expansion pressure, not a failed TPR valve. When a closed system has no expansion tank and the cold-water inlet has a check valve or backflow preventer, heated water expands with nowhere to go — pressure rises on every heating cycle and the TPR bleeds off the excess. The fix is installing a thermal expansion tank (6-gallon, 150 psi rated) on the cold-water supply line. A TPR valve that drips constantly regardless of thermal expansion may have a weakened spring — replace the TPR valve with an exact pressure-rated replacement (typically 150 psi/210°F for Reliance residential models).

3. 3

   Reliance Anode Rod Port Weeping

   The anode rod on a Reliance water heater is threaded into a hex port on the top of the tank (or on some models, under the sheet metal top cover, accessible by removing a plastic plug). The anode rod is installed from the factory with a small amount of PTFE tape on the threads, but over years of thermal cycling, the threads can loosen or the PTFE tape can degrade, allowing a slow weep from the port. On older Reliance units (10+ years), the anode rod may be severely corroded or consumed — if the rod has corroded down to the steel core wire, it can eventually corrode through the port threads. Identify this leak: dry the top of the tank and the anode rod hex head, then check after 30–60 minutes. Weeping specifically at the hex head = anode rod thread leak. Fix: drain 3–4 inches of water from the tank to bring the water level below the anode port, remove the rod with a 1-1/16-inch socket, apply 3–4 wraps of PTFE tape to the threads, and reinstall at 40–50 ft-lbs.

4. 4

   Inlet/Outlet Fitting Leak — Heat Trap Nipples or Dielectric Unions

   The cold-water inlet and hot-water outlet connections at the top of a Reliance water heater typically use heat trap nipples — brass fittings with a built-in check valve that prevents convective heat loss. Over time, the threaded joint between the heat trap nipple and the tank port can develop a slow weep, especially in hard-water areas where mineral deposits form at the joint. Additionally, if galvanized steel or copper pipes are connected directly without dielectric unions, electrolytic corrosion can attack the fittings. Identify by drying the top of the tank completely and checking both the cold (right) and hot (left) inlet/outlet fittings for moisture after 30 minutes. A weeping fitting can often be temporarily stabilized with a pipe wrench quarter-turn, but permanent repair requires draining, removing the fitting, and reinstalling with fresh PTFE tape.

5. 5

   Reliance Electric 12-Series: Element Gasket Failure

   Reliance electric water heater models (12-Series prefix) have two screw-in heating elements that penetrate the tank wall via threaded element spuds sealed with rubber gaskets. If the gasket hardens, cracks, or if the element is over-tightened (damaging the gasket), a slow drip develops directly behind the element cover plate on the side of the tank. This leak is often confused with a tank body leak because it appears on the tank side. Confirm by removing the element cover plate and the insulation — the wet point will be at the element-to-tank interface (the rubber gasket seat), not on the tank body above or below. This repair requires a full tank drain, element removal with a 1.5-inch element socket, replacement of the rubber gasket, and reinstallation of the element at proper torque (25–35 ft-lbs).

6. 6

   Reliance Tank Body Corrosion — End-of-Life Indicator

   If systematic inspection of all external connection points confirms none is the leak source — fittings dry, drain valve dry, anode rod dry, TPR pipe dry — and water is seeping from the tank body itself, the Reliance anode rod has been consumed and the Vitraglas (glass) interior lining has failed, allowing rust-colored water to contact and corrode through the steel tank wall. Tank body leaks on Reliance models appear as rust stains on the tank exterior, often originating from welded seams near the top or bottom heads. A tank body leak cannot be repaired — the unit must be replaced. On a 10+ year old Reliance tank, this is the expected end-of-life failure mode.

Quick DIY Checks

1. 1Step 1 — Dry the entire tank exterior and do a systematic trace: before assuming any particular leak source, thoroughly dry every surface of the Reliance water heater with paper towels or shop rags — tank top, all fittings, pipe connections, TPR valve body, anode rod hex head, element cover areas, tank sides, drain valve, and the floor beneath. Leave dry paper towels pressed against each connection point and check after 30–60 minutes. The paper towel that is damp reveals the true leak source. This step prevents misdiagnosis — condensation on the tank exterior in a humid basement is often mistaken for a tank leak, and water from one leak point can run down and pool at a different location (e.g. a fitting leak at the top that pools at the floor looks like a drain valve or tank leak).
2. 2Step 2 — Diagnose and fix the Reliance plastic drain valve drip: locate the drain valve at the base of the tank — on most Reliance residential models, it is a plastic valve with a threaded cap or hose-thread outlet. Check whether the drip is coming from the plastic cap/outlet (fix: tighten or replace the cap with a brass hose-thread cap from any hardware store) or from the body-to-tank joint (fix: requires full drain and valve replacement). For a body-to-tank joint leak on a plastic valve, replace with a 3/4-inch MPT brass ball drain valve (Watts LF4RB or equivalent). Close the cold-water supply, open a hot-side faucet in the house, connect a hose and drain the tank fully, remove the old plastic valve with a pipe wrench, apply PTFE tape, and install the brass valve.
3. 3Step 3 — Diagnose and address TPR valve discharge: locate the TPR discharge pipe (a copper or CPVC pipe connected to the TPR valve on the side of the tank, running to within 6 inches of the floor). If water is dripping from this pipe: (a) check whether it only drips during and just after heating cycles — this pattern indicates thermal expansion (no expansion tank on a closed system). Fix: install a 6-gallon thermal expansion tank ($30–$50) on the cold-water inlet line, rated to match your water heater pressure. (b) If the TPR drips constantly regardless of heating cycle, the valve spring has weakened — replace the TPR valve with an exact replacement rated at 150 psi/210°F (Watts N36 or compatible). IMPORTANT: never cap, plug, or remove the TPR discharge pipe — it is a critical safety device.

1. 4Step 4 — Fix a weeping anode rod port on Reliance water heater: the anode rod hex head is on the top of the tank (on Reliance models with exposed top anode port) or under a plastic plug beneath the sheet metal top cover (on models with flush-top design). If the dry-paper-towel test confirms weeping at this hex port: turn off the cold-water supply, connect a hose and drain 3–4 inches of water from the drain valve to drop the water level below the port. Use a 1-1/16-inch socket and a breaker bar to break the anode rod loose — anode rods on older Reliance tanks are often seized from years of inactivity and require significant torque. Once removed, inspect the rod: if more than 50% of the magnesium coating is depleted (down to the steel core wire), replace it with a magnesium anode rod for Reliance (AO Smith 9962320 or equivalent). Apply 3–4 wraps of PTFE tape to the threads and reinstall at 40–50 ft-lbs.
2. 5Step 5 — Fix a leaking inlet or outlet fitting (heat trap nipple) on Reliance: the heat trap nipples at the cold-water inlet (right, blue indicator) and hot-water outlet (left, red indicator) on Reliance water heaters are brass fittings threaded into the tank top. If the dry test confirms a drip at one of these fittings: close the cold-water supply valve. Connect a hose and drain 4–6 inches from the drain valve. Use a pipe wrench to attempt a quarter-turn tightening of the fitting — this sometimes re-seals the PTFE tape thread seal. If the fitting continues to weep after tightening, it must be removed and reinstalled with fresh PTFE tape. When removing, have a bucket ready — some water will spill from the pipe above. Wrap the fitting threads with 3–4 turns of PTFE tape in the thread direction and reinstall. Also add dielectric unions if copper pipe is connected directly to the tank's steel fitting.
3. 6Step 6 — Reliance electric 12-Series: diagnose and fix an element gasket leak: turn off the 240V breaker at the panel. Confirm zero voltage with a non-contact tester at the element terminals. Remove the upper and lower element cover plates (typically 2 screws each) and peel back the foam insulation. Look at the element-to-tank interface — the element passes through the tank wall and is sealed with a rubber gasket at the element flange. If the gasket is the leak source, you will see moisture or rust staining at the element-to-tank junction, NOT on the tank body above or below. Close the cold-water supply. Connect a garden hose and drain the tank fully to the drain valve at the bottom. Remove the element with a 1.5-inch element socket wrench — apply firm counterclockwise force (elements are often thread-tight from years of service). Replace the rubber gasket (gaskets are included with most replacement element kits, or purchase separately). Reinstall element at 25–35 ft-lbs, refill tank, restore power.

Repair vs Replace

Recommended Tools & Parts

• Watts LF4RB 3/4-Inch Brass Ball Drain Valve

  Brass ball drain valve to replace Reliance factory plastic drain valve. Replace when plastic valve body leaks at tank-to-valve joint. Full tank drain required. Installs with PTFE tape. More durable and reliable than the factory plastic unit.

  $12–$22

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• Watts N36 3/4-Inch TPR Relief Valve 150 psi 210°F

  Replacement TPR (temperature-pressure relief) valve for Reliance water heaters. Replace when valve drips constantly regardless of thermal expansion cycles, or when valve is over 6 years old per manufacturer recommendation. Match pressure rating (150 psi) and temperature rating (210°F).

  $15–$28

  Buy on Amazon →

• Reliance/AO Smith Anode Rod 9962320

  Replacement magnesium anode rod for Reliance tank water heaters (1-1/16-inch hex, 3/4-inch NPT thread). Inspect every 3–5 years. Replace when more than 50% of magnesium coating has been consumed (down to steel core wire) or when anode rod port is weeping due to degraded thread seal.

  $15–$28

  Buy on Amazon →

• Camco 02142 4500W Screw-In Element with Gasket

  Replacement 4500W screw-in element kit for Reliance electric 12-Series models. Kit includes new rubber gasket — use the new gasket any time the element is removed, even if reinstalling the same element. Drain tank fully before element removal.

  $18–$35

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

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