Weird Noise Coming From Ariston 24-E Combi Boiler

[chrisdingdong]

Hello,

Weird noise coming from boiler, it's an Ariston 24 E-Combi.

It's like a hissing noise and possible condensation is present from the pipes. When I turn the water off at the stop clock it stops making the noise. The water doesn't drip on floor so think it's condensation.

I possibly believe it's due to low pressure, when resting it's just below 1 when I turn hot water on it goes to above 1. I read that's why the noise is evident.

The boiler and hot water is working as it should be.

Do I need to do anything?
Can you tell me how to increase pressure I've turned the dials by the filler loop but nothing happens.

It's working fine so don't know if I need to do anything.

Thanks

P.S pictures I've taken are too big for this post