Heating on, no hot water

[Neil Rose]

Hi , I have a conventional heating system and the hot water is gravity fed with a hot water tank in the loft and a small cold water tank to fill the heating system, also in the loft.

When the heating is on, the hot water is only luke warm. When set to water only, the water gets hot at the tap.

We had a new pump fitted about 12 months ago which is set to 40.

Any advice would be appreciated.

Thanks,
Neil