are you paying attention.
when you run a hot tap your using one feed.
when your using your shower your using two feeds from one tank.
so the tank will empty twice as quick as using the tap.
your telling me it only happens when the shower is used you loose all hot taps.
that tells me your draining the tank and then drawing in air, so when tank refills your pipework is then airlocked.
now your either goning to listern or not.
run your shower for the time it takes to have two showers or till the shower stops.
and i bet your tank is empty.
when you run a hot tap your using one feed.
when your using your shower your using two feeds from one tank.
so the tank will empty twice as quick as using the tap.
your telling me it only happens when the shower is used you loose all hot taps.
that tells me your draining the tank and then drawing in air, so when tank refills your pipework is then airlocked.
now your either goning to listern or not.
run your shower for the time it takes to have two showers or till the shower stops.
and i bet your tank is empty.