Bathtime puzzler

Gents,

I was wondering if you could help shed some light on a Hunt household phenomenon.

When I have a bath if I turn both taps on full and leave the water when the level reaches the overflow the hot water will have run out and I will have a tepid bath.

But if I fill the bath 1/4 full of hot water then 1/2 with cold water and then top up with hot water I can reach the same level but with a piping hot bath. Now given there is the same finite amount of hot water being used to fill the bath how does it mean that I get a hot bath when using the water in the latter way but not the former? I am confused.

HTF.

Of course assuming that it takes about 20 mins to do that bit with the cold water filling up on it's own!

Pretty simple. Your cold water taps discharges a much greater volume per time unit than your hot. So when running both together, you don't get the perfect results you desire. However you clearly have too much time on your hands......

Something to do with mixing cold water in with the hot water right from the start I would think.
I would imagine cold water into a half full bath of hot water will have less of an effect on the hot water than cold water and hot water mixing in equal quantities from the start.

Because you're cooling the hot flow immediately on filling in the first scenario and less so by putting a stream of cold water into a mass of hot?

Most likely the answer is that the water in your hot water tank never actually gets as cold as the cold water tap.

So in the first scenario you fill the bath with a half hot, half cold. The cold is alway the same cold temperature, the hot will slowly get cooler as you empty the tank whilst filling the bath. You end up with a mix of very cold and hot slowly moving to cold.

In the second scenario, you are only filling the bath with a quarter of cold cold tap water. The remaining 3/4s is from the hot tank. Which , although cooling, never gets cold cold.

Therefore your second scenario will result in a hotter bath!

HTH

have a shower instead...saves water and relaxes your brain from such thoughts !

Why not put the cold water in first, and then add hot water to bring it up to the desired temperature?

Because the hot water will barely raise the temperature of a mass of cold water.

This.

The hot tap runs slower maxxed out.


Put the hot on max flow. Put bucket under it and time how long it takes to fill bucket.
Put bucket under cold tap. Vary tap turns until you get it to fill bucket in same time.

Remember how many turns of cold tap this took (e.g. 1+ 3/5 turns)

Use this perfect tap turn ratio of Hot=max cold=1+3/5 to make a wonderful hot bath. With less intervention + it will fill the bath to your preferred temperature in the minimum amount of time.

Magic.