Hot water not as hot after turning heating temp down

[The Bulwell Brick]

I have a Boulter Bouderous 500 boiler that serves radiators and a hot water tank, the water temp has always been set at 56 degrees which feels about right for us.

Recently the heating has been on timed for twice a day and extras hours used as and when needed, I read the gas meter over a 24 hour period then reduced the heating temperature down and put it on constant. I read the meter after another 24 hours and found that it used the same amount of gas, which is great apart from the fact that since I turned down the heating temp, my hot water is now only just warm enough to wash in despite the water temp still being set at 56 degrees.

Anyone got an idea why this is, it just doesn't seem right?

 

[ShaunCorbs]

Because your boiler temp is reduced this heats your hot water so reducing this is a bad idea and a good idea for legionella growth

 

[The Bulwell Brick]

Because your boiler temp is reduced this heats your hot water so reducing this is a bad idea and a good idea for legionella growth

but I've only turned the heating down, the water temp is still set at 56 degrees - why does the heating temp affect the water temp? I'm aware of the legionella dangers.

 

[Gasmk1]

Because the water will only get as warm as the boiler temp you have set

 

[The Bulwell Brick]

Because the water will only get as warm as the boiler temp you have set

OK, maybe I'm being a bit thick, that makes sense but why do I have 2 temperature settings? Just seems a bit mental that in order have my water hot I have to have the house too hot. I turned the heating temp down in order to have the heating on constant because having it set on timer and putting it on as and when it was needed was a real pain, my home is old and despite being insulated and double glazed it loses heat at a fast rate so it has to work harder to bring the temp back up.

 

[tamzbackforalook]

Because your boiler temp is reduced this heats your hot water so reducing this is a bad idea and a good idea for legionella growth

Reducing temperatures below 65 isn't wise when you have a hw cyl, no matter what they say on the telly. Keep it at that at least once a week.
To Shaun.
Can you provide one proven case of domestic legionella in the UK?