"Ice bath" shower mixing valve question

[TomL]

My teenage son, while training for cross-country, developed a calf injury. An "ice bath" is one way to reduce pain and inflammation following an injury. The first time he did an ice bath, we found that turning the mixing valve for cold water, it didn't seem so cold. I figured it was mixing in some hot water, even on its cold setting. So, this time I decided to turn off the hot water supply, so only cold water was feeding the house. To my surprise, the cold water just dribbles out. Yet, turning on the cold water for the sink right next to the bathtub, there is plenty of flow. So, I went to our master bathroom shower, and in that case there was even less flow of cold water. There again, those sinks there have plenty of flow of cold water. Then I tried the kitchen sink faucet that has a mixing valve. It has plenty of flow.

I've come to the conclusion that shower mixing valves must be designed this way.

I would like to understand why, and how they are made to work in this manner.

Thanks.

 

[Terry]

You have "pressure balanced" shower valves.
Designed to prevent scalding when someone flushes a toilet ore uses a sink while someone is in the shower.
When you turned off the hot water, it balanced the valve. No hot means no cold.

 

[Sponsor]

 

[TomL]

Thank you for the quick and clear explanation Terry. It makes perfect sense now.

Possibly I was imagining that warm water was mixing in on the cold setting on our first attempt at an "ice bath."

Using the phrase "pressure balanced", I found this helpful link...

https://www.hunker.com/13717893/what-is-a-pressure-balance-shower-valve

...and I learned about thermostatic valves.

If we had a thermostatic valve, I'm *presuming,* given the same set of conditions, we wouldn't have had just a dribble.

 

[Jadnashua]

Many thermostatically controlled valves can achieve an all-cold situation, but not all. SOme two handle, pressure balanced ones might be able to as well, but no single handled ones generally allow all cold that I've seen.

In the interim, you might just need to go buy a 10# bag of ice when he wants to soak his leg!