small valve on cold water supply ahead of water heater?

(Walt Hoffman) #1

Could someone please tell me what the small brass valve on the cold water supply at the water heater is and what its purpose is? It has a plastic drain line to the water heater pan. Is it normal to be releasing/draining water continually? Thank you for any info.

(rmoore) #2


It doesn't look like any trap primer I'm aware of so I'm guessing it's a calibrated pressure (only) relief valve. It looks similar, but not the same, to this one from Watts .

They are sometimes used along with a Watts gas valve in situations where a normal TPR valve discharge line would be difficult.

As I said, just a guess. Screwy thing doesn't make any sense to have it draining to the water heater pan. If you're going to do that then a normal TPR valve would do. Also the one in the photo doesn't look big enough if it is the pressure relief. And then there's the plasic tubing??? :shock:

Anyway...a big NO for it to be releasing water continuously, no matter what it is. Something would be wrong...either the valve or the pressure.

(Ted Allen) #3

I do not know what it is , but it just looks wrong.:neutral:

(William R. Cottrell) #4

I think you will find the valve is mfg by Conbraco and is a pressure releif valve or thermal expansion valve.
South Carolina had just approved them to replace expansion tanks for the water heaters. RV 78 comes in many sizes and pressure settings.

Regards Bill

(system) #5

It looks like a supply line for a refrigerator>

(rmoore) #6

Thanks for the info Bill,

So it's a combination supply shut-off and thermal expansion relief. Used with a normal TPR valve.

Never seen one before. Thermal expansion tanks are the vogue around here.

And...plastic aquarium tubing to the drip pan still seems wrong.

Walt, you said it was releasing/draining continually. Do you know what the supply pressure was?

(William R. Cottrell) #7

The plastic supply is determined by the AHJ. In SC they had to be copper piped to the exterior of the house. If the unit is working correctly it should discharge water periodically to releive the expansion of water due to the heating of water, just as the bladder would compress the air in the expansion tank.

Regards Bill