Thread: Under Sink Plumbing

Saw this arrangement under the upstairs master sink in a house built on a slab. What is this about?

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SS: It appears to be a backflow valve installed by simians.

type of back flow device

No, that's a mixing valve or "tempering" valve. It mixes the hot and cold to prevent scalding, as the water temperature output is set by the knob. Some people use them for toilets to prevent condensation on the tank.

Wilkins Mixing Valve

Dom.

Dom,

I noticed on the label it states that the valve should never be installed that the user could change the setting.

Being mounted as such in a cabinet, a child could easily change the setting don't you think?

Just a observation.

rick

Thank you, gentlemen.

Appears to be a thermostatic (tempering) mixing valve (wilkins/zuni aqua-gard) but what else its supplying don't know (hot water continues down under the sink stop valve) - a second sink, perhaps a toilet tank to prevent sweating, or a bidet.

I'd guess domestic hot water via boiler/tankless or storage type water heater with very hot slugs during boiler firing cycles for heat, or intentionally kept at a higher temperature to prevent bacteria growth (140) and maintain temperature through slab in cold months, which must be tempered at point of use to prevent scalding.

LOL in the time it took me to type you already had several replies. Should have said tempered domestic hot water continues down under the stop valve.

Originally Posted by H.G. Watson, Sr.

Appears to be a thermostatic (tempering) mixing valve (wilkins/zuni aqua-gard) but what else its supplying don't know (hot water continues down under the sink stop valve) - a second sink, perhaps a toilet tank to prevent sweating, or a bidet.

I'd guess domestic hot water via boiler/tankless or storage type water heater with very hot slugs during boiler firing cycles for heat, or intentionally kept at a higher temperature to prevent bacteria growth (140) and maintain temperature through slab in cold months, which must be tempered at point of use to prevent scalding.

HG: I have only seen these installed at water heaters, never under sinks.

Is there a bidet in the bathroom ?

Originally Posted by A.D. Miller

HG: I have only seen these installed at water heaters, never under sinks.

I have seen these far and remote at bathroom groups (2 per) and kitchen sinks.

With advent of CPVC and PEX plumbing the anti-bacterial properties of copper supply are lost.

See most often with boiler supplied water heating or water heater storage tanks being dually used to supply hydronic heat.

Consumer wants higher temperature domestic hot water to supply dish washers, washing machines, especially when heat sinks like slab foundations, and desires higher temperature water in the supply system - i.e. above 135 some health experts recommend 140 to prevent legonella and other nasties from continuing to grow in the water supply, then temper at point of use or at the bathroom group.

Most often see behind accessible plumbers door, set in the wall such as those made by watts and others, but under a sink cabinet is not unheard of in a master bath vanity cabinet for the sink(s) and/or bidet and possibly a sink on the other side of the second story wall for the children's bathroom.

You would want the higher temperatures maintained in the distribution system tempering off only at use locations.

That is a good idea for a bidet, you don't want to burn your junk