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The Distribution Tempering Control valve Scheme (DTC)

With the proliferation of storing water at high water temperatures i.e. above 60°C or having a storage vessel capable of storing hot water at a temperature exceeding 80°C valves capable of reducing the water supply temperature to a more acceptable distribution temperature must be fitted adjacent to the hot water storage vessel.

Building Regulations

This requirement is now included within the Communities and Local Government Building Regulations 2000 Sanitation, hot water safety and water efficiency, Approved Document Part G.

The approved Document G (2009) comes into force on the 1st October 2009 and supports the Building Regulations 2000 (SI 2000/2531).

The Approved Document Part G states: -

Where the operating temperature of domestic hot water in the storage vessel in the storage vessel in a dwelling is capable of exceeding 80°C under normal operating conditions (a situation that may occur in vessels used as heat stores and those connected to solar heat collectors or solid fuel boilers that do not have intervening controls between the boiler and the vessel containing the hot water) the outlet from the storage vessel should be fitted with a device, such as an inline hot water supply tempering valve in accordance with EN15092, to ensure that the temperature supplied to the domestic hot water distribution system does not exceed 60°C.

Requirements of the Scheme

The Distribution Tempering valve Control Scheme (DTC Scheme) independently verifies that tempering valves comply with the minimum requirements of the Building Regulations part G and additionally ensures that the valves and the approval holders continue to meet these requirements throughout the valves approval period (5 years).  The Scheme also requires additional information to be provided with the tempering valve to enable the valve to be installed and maintained to ensure correct operation.

EN15092 specifies dimensions, materials and performance requirements (including methods of test) for in line hot water supply tempering valves for sanitary hot water systems, of nominal sizes from DN 15 to DN 50.

Tempering valves reduce the temperature of sanitary hot water for distribution throughout the hot water system and are intended to be used with storage water heaters to provide tempered hot water to the terminal fitting. They are not intended to control the temperature at the point of use i.e. they are not safety devices, thermostatic mixing valves that are TMV2 approved must be used to control the temperature of water at the point of use.

Tempering valves can be either non-adjustable tempering valve with pre-set temperature (Type 1 valves) or adjustable with or without tool and with pre-set temperature (Type 2 valves).  The standard EN15092 suggests that valves should be capable of distributing water at between 45°C and 65°C however the Water Supply (Water fittings) Regulations 1999 state that the hot water must be stored at a temperature of greater than 60°C and distributed at a temperature of greater than
55°C.

Therefore the Distribution Tempering valve Control Scheme (DTC Scheme) verifies that valves comply with the requirements of EN15092 (excluding acoustic requirements) and in addition additional performance tests conducted between 55°C and 60°C to verify compliance with the requirements of the Water Supply (Water Fittings) Regulations 1999.