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requirement for a mixing valve in a domestic house

requirement for a mixing valve in a domestic house

requirement for a mixing valve in a domestic house

Hi all,
the heating system in a bungalow that uses an Air to Water heat pump has a TMV (thermostatic mixing valve) at the outlet from the DHW tank. It is a gravity system. While the shower is pumped and there is no bath, the TMV is likely to impact on the flow to the WHB and Kitchen sink.

Can the TMV at the outlet from the DHW tank be left out?

Looking at Irish Building regulations, there does seem to be a requirement to fit a TMV. In UK Regs Sanitation, hot water safety and water efficiency Part G, a bath needs a TMV and CIBSE reference the need for TMVs in NHS/care type buildings,

Perhaps TMVs are not needed in Irish Houses?

RE: requirement for a mixing valve in a domestic house

TMV's are usually needed for environments where the users lack the knowledge and/or ability to avoid potential injury. They aren't - as far as I'm aware - mandatory in all applications. Who are the likely users of the system?

RE: requirement for a mixing valve in a domestic house

What limits the max water temp in the system?
If there is no other limit then a TMV is prudent.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: requirement for a mixing valve in a domestic house

It depends.
What is the temperature of the water in the water heater? If it is above 120°F then a TMV will be needed to prevent scalding water at sinks (kitchen and bath).
If the local water authority has concerns about legionella or other bacteria in the water, it would be resonable to store water at ~140°F.
TMVs at tubs/showers are required by a lot of codes since that is where most water burns occur in the house. (120°F can still burn and infants are especially suseptable). When installed here, they are frequently called out as "anti-scald" device.

Read your code again and see if it says where exactly the TMV is required.
Read also the literature on the HP water heater, manufacturer may require the TMV.

RE: requirement for a mixing valve in a domestic house

The following document might help - see page 9. https://assets.publishing.service.gov.uk/governmen...

Also, Part G is quite specifically addressing the hazards of baths full of potentially scalding water, viz:

3.65 The hot water supply temperature to a bath should be limited to a maximum of 48°C by use of an in-line blending valve or other appropriate temperature control device, with a maximum temperature stop and a suitable arrangement of pipework.

No mention of water supply to a shower.

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