Losing steam power on the steam buggy?

I use my steam buggy once in while mainly for good deep cleaning in the kitchen
I haven't use it for 3 months and it seems to be losing steam power, steams not flowing stronge & there's a lot of water dripping while it's been used.
I am not sure how to improve the steam flow and I don't really want to damage the steam buggy!!!
Has anyone experience a similar problem or got any solution to my problem????
Many thanks S