Rheem Marathon MR105/473185

Questions and Answers

S
Shawn VillaAug 7, 2025
What to do if Rheem Marathon MR105/473185 Water Heater leaks?
- J
  Jennifer DavisAug 7, 2025
  If your Rheem Water Heater is leaking, there are several potential causes. First, check for loose connections between the inlet/outlet piping, relief valve, or drain valve and the hex nut union on the tank fittings; tighten the hex nut union fitting if necessary. Second, inspect the seal rings and replace them if damaged. Finally, examine the gasket around the heating element(s) and replace it if needed.
M
Melanie WellsAug 17, 2025
Why is Rheem Marathon MR105/473185 Water Heater water too hot or not hot enough?
- C
  clarkdavidAug 17, 2025
  There are a couple of reasons why your Rheem Water Heater might be producing water that is too hot or not hot enough. One potential cause is that the thermostat access panel(s) and/or insulation are not in place; inspect and replace these as needed. Another possible cause is that the thermostat(s) are not resting tightly against the mounting plate; inspect and ensure that the retaining spring(s) or mounting screws hold the thermostat(s) tightly to the mounting plates.
M
mboydAug 27, 2025
How to fix noisy heating elements in Rheem Water Heater?
- L
  Laura AndersonAug 27, 2025
  Noisy heating elements in your Rheem Water Heater are often due to scale build-up on the elements. The suggested solution is to remove the elements and clean them.

Summary

General Safety Precautions

WATER TEMPERATURE ADJUSTMENT

Discusses setting water temperature for safety and energy conservation, and scalding risks.

DANGER: SCALD POTENTIAL

Highlights risks of hot water and advice for vulnerable groups like children and the elderly.

WARNING: INSTALLATION SAFETY

Emphasizes crucial safety steps during installation, including T&P valve and electrical hazards.

Introduction

LOCAL INSTALLATION REGULATIONS

Information on adhering to local codes, utility requirements, and the National Electrical Code.

LOCATION

Guidance on selecting an appropriate, clean, and dry installation site for the water heater.

Installation

INSPECT SHIPMENT

Verifying the water heater for damage and checking the rating plate against the power supply.

THERMAL EXPANSION

Explains pressure increase from heating water in closed vs. open systems.

WATER SUPPLY CONNECTIONS

Details on connecting hot and cold water lines, including shut-off valves and pressure regulators.

RELIEF VALVE AND DRAIN PIPE

Instructions for installing the temperature and pressure relief valve and its discharge pipe.

DRAIN VALVE AND FILLING

Steps for operating the drain valve and filling the tank completely with water.

ELECTRICAL CONNECTIONS

Guidance on wiring the unit to the power supply via the junction box.

TIME SWITCH;OFF-PEAK METER CONNECTION

Specific wiring instructions for connecting to energy management systems.

PIPE WRAP ENERGY KIT

Instructions for applying the included insulation kit to hot and cold water pipes.

Installation Check List

A summary of required installation steps and checks for proper setup.

Operation

SAFETY PRECAUTIONS

Essential safety rules for operating the water heater, including power and water supply.

WATER TEMPERATURE SETTING AND THERMAL PERFORMANCE

Explains how water temperature affects performance, efficiency, and potential issues.

WATER TEMPERATURE SETTING

Guidance on selecting and adjusting water temperature for safety and energy savings.

RESETTING THE UPPER THERMOSTAT

Step-by-step guide to access and adjust the upper thermostat settings.

RESETTING THE LOWER THERMOSTAT

Step-by-step guide to access and adjust the lower thermostat settings.

SAFETY CONTROLS

Information on the high temperature limit switch and its manual reset procedure.

EMERGENCY INSTRUCTIONS

Actions to take if the water heater is subjected to flood, fire, or physical damage.

VACATION AND LONG TIME SHUT-DOWN

Procedures for periods of non-use, including draining to prevent freezing.

DRAINING THE WATER HEATER

Detailed instructions on how to safely empty the water heater tank for maintenance or storage.

Maintenance

ROUTINE PREVENTATIVE MAINTENANCE

Recommended regular checks and actions for upkeep, including cleaning and safety checks.

REPLACING THE TEMPERATURE & PRESSURE RELIEF VALVE

Detailed steps for safely removing and installing a new temperature and pressure relief valve.

HEATING ELEMENTS

Instructions for replacing burnt-out heating elements, including safety precautions and part identification.

Trouble Shooting Guide

No Hot Water

Diagnosing and fixing common causes for a lack of hot water supply.

Not enough Hot Water

Troubleshooting issues related to insufficient hot water output.

Water too hot or not hot enough

Addressing problems with water temperature regulation, including thermostat settings.

Noisy heating element(s)

Identifying and resolving noises, such as rumbling, attributed to heating elements.

Water Leaks

Diagnosing and fixing common points of water leakage from the unit or connections.

This document is a comprehensive Use & Care Manual for Non-Metallic Electric Water Heaters, specifically residential electric models with capacities ranging from 30 to 105 gallons. It includes detailed installation instructions for installers and operational, safety, maintenance, and troubleshooting information for owners and operators.

Function Description:

The device is a non-metallic electric water heater designed to provide hot water for residential use. Its non-metallic construction aims to prevent rust and corrosion, promising extended service life. The water heater is fully assembled and ready for installation upon purchase.

Important Technical Specifications:

Capacity: 30 - 105 Gallons (Residential Electric Models).
Electrical Requirements: Operates on 240V power source. Specific wattage load is indicated on the rating plate.
Temperature & Pressure Relief Valve: Factory-installed, designed to automatically open if temperature reaches 210°F or pressure reaches 150 PSI. The BTUH rating of the relief valve must not be less than the input rating of the water heater (1 watt = 3.412 BTUH).
Vacuum Relief Valve: Factory-installed in the cold water inlet line to prevent vacuum or negative pressure in the tank, which could occur due to main water supply line breaks, pump failures, or other plumbing malfunctions.
Thermostats: Dual element heaters have two adjustable surface-mounted thermostats located behind jacket access panels. Factory-set at 120°F (or lower if local codes require).
High Limit Switch (ECO): A combination thermostat and high temperature limit switch located above the upper heating element. It breaks the power circuit to the heating element if water temperature becomes excessively high and requires manual reset.
Insulation: The water heater tank is insulated with 2 1/2" of foam insulation to minimize heat loss. An optional pipe wrap energy kit is provided for additional insulation of exposed pipes.
Drain Valve: Factory-installed for draining the water heater.

Usage Features:

Water Temperature Adjustment: Thermostats allow adjustment of water temperature. The upper thermostat is recommended to remain at the factory setting (120°F) for most normal applications, with adjustments primarily made at the lower thermostat. Temperature settings range from approximately 110°F (LOW) to 170°F (HI), with MED corresponding to about 140°F.
Safety Precautions: Emphasizes the importance of reading the manual, understanding scalding risks (chart provided for time/temperature relationships in scalds), and ensuring the water heater is completely filled with water before turning on power to prevent damage to heating elements.
Emergency Instructions: Provides guidance for situations where the water heater has been subjected to flood, fire, or physical damage, advising to turn off power and water and seek qualified service personnel.
Vacation and Long Time Shut-Down: Recommends turning off power and water, and draining the water heater and piping if freezing temperatures are expected, to conserve energy and prevent damage.
Energy Efficiency: The non-metallic construction and foam insulation contribute to energy efficiency. The pipe wrap energy kit further enhances energy savings by insulating exposed pipes.

Maintenance Features:

Routine Preventive Maintenance:
- Noise Inspection: Suggests inspecting for excessive hissing or singing sounds, which may indicate the need for heating element cleaning.
- Clearance: The area around the water heater must be kept free of flammable liquids and combustible materials.
- T&P Relief Valve Operation: Recommends lifting and releasing the lever handle on the T&P relief valve at least once a year to ensure free operation and flush the discharge line.
- Tank Draining: Advises draining a few quarts of water from the tank once every month to remove accumulated solids (sand, silt, dirt, mineral scale).
Replacing the Temperature & Pressure Relief Valve: Provides detailed steps for safely replacing the T&P relief valve, including turning off power and water, draining the tank, removing the old valve, installing a new valve with a seal ring, and reconnecting the discharge pipe. Emphasizes using only specified valves and avoiding direct heat application during installation.
Heating Elements Replacement: Offers instructions for replacing burned-out heating elements, including safety precautions (turning off power, draining water), removing access panels and insulation, disconnecting wires, removing the old element, installing a new element with a gasket, refilling the tank, and reconnecting wiring. Stresses the importance of using proper replacement elements specific to the lower and upper positions.
Troubleshooting Guide: Includes a table outlining common problems (e.g., "No Hot Water," "Not enough Hot Water," "Water too hot or not hot enough," "Noisy heating element(s)," "Water Leaks"), possible causes, and recommended service actions. It strongly advises against attempting electrical wiring, thermostat, heating element, or other operating control repairs by unqualified personnel.