question on second floor hot water being hot all the time

[James23912]

I have a jet tub bath on the second floor fed thru pex, I usually turn on the water normally and never check it but today I went to just rinse off some paint and turned on the hot water knob and hot water came out right away. I don't understand, it would imply a leak somewhere but I have been in the house for 3 years and no leakage I am aware of, it seems strange. I did check and I see that the hot line for the tub is the first one on the manifold so I am wondering if that would keep hot water pushing upstairs? I have yet to get the sink hooked up but there is a second bath next to this one and the hot does not come on right away.

 

[Fitter30]

Wonder if it has a built in booster heater.

 

[Sponsor]

 

[James23912]

no, no heater

 

[Nate E]

If the mixing valve has internal leakage between the hot and cold side, water can circulate through the branch due to fluctuations in pressure between hot/cold.

This happens when rough ins are installed without the plugs that isolate hot and cold.

Nate