Water Pressure Mystery

[Henry7]

The water pressure coming into the house from the mains is approx' 80psi.
I was getting knocking in the pipes, after United utilities repaired a leak outside my house and the pressure went up.When you turned taps off in the house and outside tap at the back of the house, the knocking would occur.
I had a pressure reducer fitted where the mains water pipe first appears in the garage, to reduce the pressure to approx' 60psi.
As soon as the gauge was fitted the knocking stopped.
However when I check the pressure at the outside screwed tap at the back of the house it reads 80 psi??
I have a couple of pressure guage's and both say 80 psi?
How can this be?

 

[terryplumb]

If you close your mains internal stopcock ,does the outside tap still work ?

 

[Henry7]

If you close your mains internal stopcock ,does the outside tap still work ?

No.
The outside tap comes off the kitchen pipe.
If I run the cold tap in the kitchen, the outside tap pressure drops to 45psi.