How to check if storage tank is supplying combi boiler, help

[Hensh1974]

I was wondering if anyone could help?
We recently bought a first floor flat and found that there was a cold water storage tank in the loft that is still being fed by a water supply.....the issue is that we have a combi boiler and I thought this would have been fed by the mains rather than storage tank......would this be the norm? I believe the kitchen and bathroom taps and toilet flush all run off the main so I can't see what else the storage tank would be supplying....
I was thinking about running the hot water taps to see if the level dropped in the storage tank, then I'm guessing this would prove that it does feed the boiler......is this right?

Also if the storage tank is supplying the combi, how much would it cost to drain the tank and have the boiler connected to the mains?

Any help greatly appreciated

 

[Charnwood]

The tank could be supplying the ground floor flat.
When you buy a top floor flat the loft is not, as a matter of course, included in the sale.

 

[Madrab]

The easiest way to check if anything is running off that tank would be to turn off your mains stop cock and then run all your taps, if anything still runs then it's possibly tank fed.
The best way though would be to turn off the mains at the street and see if anything still runs. Just let everyone in the building know before you do it.
Can you see how many distribution pipes run from the tank? These tanks sometimes fed more than one flat, so need to check just in case it is still being used by another property.
If the tank isn't being used then it should be decommissioned as it's a few hundred litres of stagnant water just waiting to fall through the ceiling.

 

[Hensh1974]

We do own the loft space so I would hope that the tank doesn't supply the ground floor flat but I need to check with the owner below.....so far I've been unable to locate mains stopcock.....I Intend to check where the storage tank outlet pipe goes properly at the weekend, after a quick look with a torch yesterday the pipe seems to go in the direction of the boiler