Don’t understand how the plumbing works. I keep thinking the water should already be hot.
In: Engineering
To clarify, you mean if you run the tub to warm the water up, then pull the lever (or use whatever method your tub uses to switch from the faucet to the shower head), why does the water initially come out cold?
If accurate – the shower head is usually a few feet, at minimum, above the faucet…so while the the water and pipes up to the faucet level is warm, it cools a little when it suddenly has to flow through cold pipes up to the shower head. In my experience though this cooling doesn’t last very long, like a second or two max before it warms back up.
The pipes are usually cold and often an on demand water heater needs to turn itself on. The closer the bathroom is to the water heater/tank, the faster the water will heat.
Because there is still some water in the pipes between the main (the one that feeds the bath and the shower) and the shower head itself. That water has cooled down since your last shower, and it gets pushed out first when you turn the shower on. Then the warm water from the main reaches the head, and it feels warm.
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