High risk
You feel a shock from a light switch, even a brief one. Stop using that switch, do not take the faceplate off, and have the circuit tested before anyone uses it again.
Emergency
Stop using every tap and metal pipe. In England, Scotland and Wales call 105, and call an emergency electrician. Call 999 if someone is unconscious or not breathing normally.
A washing machine, dryer, fridge or other appliance gives a shock or tingle from the metal case, even a brief one. Do not open the plug, and unplug it only if you can do that without touching the case.
You get a shock from a socket faceplate, or while putting a plug in. Stop using that socket, do not open it, and have it tested. If taps or radiators do the same, call the electricity network on 105 as well.
A radiator or heating pipe gives a shock, even a brief one. Keep off the heating metalwork and the taps. The main switch does not make those pipes safe.
Low risk
A brief snap from a door handle after walking on carpet is consistent with static from dry air. It is not proof. A shock from a tap, socket, switch or appliance needs checking even if it was brief.
Caution
A shock from pipes, a window frame or an appliance case needs testing, including when it was brief. A snap from a door handle after friction is only consistent with static, not proof.
Stop using the shower and the taps. Call an emergency electrician. Call 999 if someone is unconscious or not breathing normally.
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