is there air in my hotwater system

[jimmig]

When i try to fill my bath with hot water, the hot water runs normally filling the bath about 6 inches deep, the hot tap then runs very slowly with luke warm water.
Is this air in the system and if so how can i get rid of it?

 

[oilman]

What sort of system have you got?
What sort of boiler is it?
Do you have a hot water tank?
How big is it?
How big is your cold water tank?
What else can you tell us?

 

[jimmig]

What sort of system have you got?
What sort of boiler is it?
Do you have a hot water tank?
How big is it?
How big is your cold water tank?
What else can you tell us?

The boiler is only a year old it's a halstead hero 65btu conventional type. The system is old though, the boiler is upstairs and the hotwater tank is downstairs.
There is a pump on the system and a changeover valve, i think it's the 'Y' type pumped arrangement.
Not sure of the capacity of the hot water tank, will there be a label on it with the capacity?
The cold water tank in the loft isn't huge but i'm not certain of the capacity without going and measuring it. what would be the normal ratio for these things?
could a lack of capacity be the problem? the worrying thing is the way the hot tap just becomes a really slow flow.
Any thoughts would be appreciated