Lack of Hot Water!

[Majesticflyer]

Hi All,
I got back from my holidays last week and i put my Ideal Elan 2 boiler on to "twice daily" central heating CH and Hot water HW settings (individual selectors on Horstmann Diodime timer ((and both were off for my week holiday))...
It seems i only have limited amounts of Hot Water. It comes out hot initially but after a couple of litres it is lukewarm at best and not nearly enough for a bath, only enough to fill a wash basin.
If I select water heater on constantly the water is hot enough for a bath after a few hours but i never had to do this before to get a bathfull of warm water.
Have i got some kind of Thermostat in the hot water tank that has failed or something?

thanks for taking the time to help

 

[diverdee]

make sure nobody has turned stat down at boiler

 

[gas4you]

What about your CH? If this is dodgy check your pump hasn't stuck whilst you were away.

 

[Majesticflyer]

Hi Guys,
Thanks for the quick replies.
The central heating is just fine (sorry i forgot to mention that at the start!!).The pump is very warm and making a noise and all radiators are warm so its ok too. (I have a gravity system)
I checked the stat setting, its a drayton cs-2 unit and goes between 2 and 9 on the scale a large mark on the stat indicates between 5 and 6 . I presume this is the 60 degree point.. I turned the stat up to 6.5 so i will see if that makes a difference.
I really can't fault the 20 year old system before now..maybe i should join British gas assistance or the other one provided by Scottish Hydro............
I bled some radiators today as well and noticed the water was quite black..Is this normal?
cheers for all your help

 

[HDPete]

Now I am no expert, but this may help....

I had exactly the same issue after returning from holiday. It turned out that my heat exchanger was completely furred up from limescale (we are in a very hard water area). It seems that the prolonged period of no flow allowed it to harder quicker.....

Those in the know... Am I talking rubbish??