Watts 210-5 automatic gas shutoff valve on a gas fired water heater (c) DelCerro Automatic Gas Water Heater Shutoff Valves

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Automatic LP, Propane or Natural Gas Shutoff Controls & Valves for water heater:

This article series describes the installation, function, & safety of automatic gas line shutoff valves used on water heaters, such as the Watts 210-5 series automatic gas shutoffs. Water temperature that is unsafe turns off the gas supply to the gas burner.

Our page top photo shows a Watts series 210-5 automatic gas shutoff valve installed in the TPR valve tapping on the side of a gas-fired water heater. The gas piping that is to run into and out of this valve has not yet been installed.

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How & Where Locate & Inspect Natural Gas or LP Gas Fuel Shutoff Valves

Automatic Gas Shutoff Valves on Water Heaters

Watts 210-5 automatic gas shutoff valve on a gas fired water heater (c) DelCerro

Shown at page top and again here is a Watts 210-5 automatic gas shutoff valve installed at the temperature-pressure relief valve on a gas fired residential water heater.

The gas piping had been removed when this picture was taken by our reader (Anon) in 2017 .

Gas supply piping in a completed installation is passed through the Watts 201-5 and onwards to the water heater's own gas controls and burner as we will illustrate in sketches below.

This automatic gas shutoff valve for water heaters may be installed in three situations:

  1. Install the automatic gas shutoff in the water heater's TPR valve tank side or tank top tapping.

    The Watts 210-5 Shutoff may be installed right into the Temperature-Pressure-Relief valve tapping on the side of a water heater if the heater was not provided with a conventional temperature/pressure relief valve already installed in that location.

    See RELIEF VALVE, WATER HEATER for details about conventional TPR valves on water heaters.

    (Sketch below, adapted from Watts 210-5 regulator installation instructions cited below)

    [Click to enlarge any image]

Watts 210-5 automatic gas shutoff control on a gas fired water heater (C) InspectApedia Watts regulator

Watch out: in our OPINION, though you may find older water heaters in this configuration, water heaters with a remote TP valve - that is a TPR valve connected to cold water inlet (1 in the sketch) or possibly to hot water outlet piping (2) - are less safe than those with a TPR valve in the factory-designated tank side or top tapping intended for a relief valve. But in all of these installations adding the Watts 210-5 will increase the safety of the water heater.

Watts Regulator's installation instructions include this safety warning:

A pressure relief valve must be installed as shown to prevent excess pressure by thermal expansion.

There must be no valve between the relief valve and heater. Relief valve must be piped to a suitable drain.

Relief valve must be located in an area that is not subject to freezing. Removal of the factory installed T&P valve may void water heater manufacturer’s warranty.

  1. The Watts 210-5 may be installed into the top of a tee in the hot water outlet piping at the top of a water heater if the heater already has a conventional TPR valve installed on the water heater at its side tapping. The probe of the gas shutoff valve will pass down through the tee into the top of the water heater. (Sketch below)

Watts 210-5 auto gas shutoff installed atop a water heater having a pre-existing TPR valve (C) Watts Regulator Co.

  1. The Watts 201-5 may also be installed into the side tapping on a water heater tank (intended for a conventional relief valve) if instead of a conventional TPR valve the water heater uses a "remote" relief valve on the hot water piping above the heater. This installation is shown in our page-top photos.

Functioning similarly to a water heater "TPR" or "temperature-pressure-relief valve this control will respond to an unsafe, too-hot water temperature by shutting off the gas supply to the water heater.

The Watts 201-5 valve shown will shut off the gas supply if water temperature exceeds 210°F. The valve uses a "snap action latch" to secure the gas supply in the OFF position. The white button at th valve top is a manual reset that must be operated if this valve has shut off the gas supply.

Our second image of the Watts 210-5 automatic gas shutoff valve just below, adapted from Watts literature, shows the key components of this control.

Watts 210-S automatic gas shutoff valve showing components (C) Watts Corporation

Here is Watts Regulator Corporation's description of their 210-5 Series water heater gas line safety control:

Series 210-5 Automatic Gas Shutoff Valves are used in gas water heater applications to protect against overheating water in the domestic hot water supply heating system. It is an immersion-type valve that automatically shuts off the gas supply to the heater if the temperature reaches 210°F (99°C).

It is a self-contained device that consists of Buna-N disc-to-metal seating, manual reset button to reopen the valve after an automatic shutoff, trip latch assembly and stainless steel spring seats to close the valve at a controlled temperature, and thermostat with extension tube which operates trip latch in response to water temperature.

Design certified by CSA. Models L210-5 M2, LL210-5 M2 and LLL210-5 M2 feature extended shanks for use with water heaters containing extra thick insulation, up to 3 in.  - Watts Corporation cited below.

This valve is sold in various models with temperature probes of varying lengths to accommodate water heaters with various thicknesses of insulation:

Contact the Watts Regulator Corporation


Continue reading at RELIEF VALVE, WATER HEATER - home , or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see GAS SHUTOFF VALVES including fire safety valves that shut off gas supply to a heating appliance or water heater



Or see WATER HEATER SAFETY for our complete list of water heater safety devices and water heater safety inspection advice.

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AUTOMATIC GAS WATER HEATER SHUTOFF at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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