some taps air locking?

[mbrad]

hi all, at risk of sounding a numpty can "some" taps air lock whilst others are fine in same room?
this is a standard gravity hot water system that feeds 1 bathroom, 2 ensuites, kitchen and cloaks, there is a seperate cold feed from tank to bath cold and a sepertate feed to shower which i have just installed, the hots all run from the cylinder an 22 to t5he bath and 15 to everything else.
my problem is that 2 basin hots are runnning really poorly but everything else is fine. the shower doesnt run great either, which is causing my customer some concern, its standard bar shower that is supposed to be suitable for gravity systems. the shower over the bath runs great but there are 2 x 22mm feeds to the bath.
any help in getting the issues resolved would be great, both basins are new so dont know if it was bad before.
the house is 9 years old and done in plastic pipe. hope i have given enough information.
many thanks

 

[seco services]

what are the taps on the new basin ? low pressure etc.
you say the shower has its own cold supply.
but the hot comes from the other supplies bath etc ?

why hasn't the shower got its own hot supply ?

 

[fingertight]

Simplist (and supprisingly common) thing to try first is check basin taps spout end, nearly all taps now are fitted with filters at the end of the spout, try removing them as they can dramatically restrict the flow (they just unscrew). If you fitted iso valves on basin supplies were they "full bore" iso valves? Having full bore iso's would help as normal iso's restrict flow also. This is all small stuff though...

A must for mutiple draw offs on a cylinder is an essex or york flange..is the cylinder fitted with one, if not, it will need one, then for safe keeping I would find out where the 22mm hot reduces down to 15mm for your new shower, and increase both feeds to new shower to 22mm. Hope this helps.

 

[mbrad]

the taps had already been fitted so dont know whether high or low pressure, however the cold suply is fine, direct from the cold main.
the hot just comes direct from top of cylinder, tees for vent an runs to bath in 22mm and i assume just tees off for other supplies. i didnt run a fresh feed from cylinder as it would have meant going through 2 bedrooms removing chipboard floors! cost and time the customer didnt want. the other taps in house are all pilar taps except kitchen bathroom and ensuite.