This is what I've learnt this afternoon:
- The boiler and shower water heater need to be on (which they are all the time anyway)
- Then fill the bath up about a quarter of the way up
- Turn the hot tap off and get in
- Catch my breath
- After about 15 minutes (to let the boiler fill back up and heat the water again) turn the hot tap back on and fill the bath until it's about half full
- about 15 minutes later, fill the bath up to about three quarters full
- When I notice the water cooling down a bit (roughly half an hour), empty the bath out to about a third of the water
- repeat as required!
The important thing is to NOT use all the hot water in the boiler straight away... don't rush things otherwise the water will run cold because it hasn't had a chance to re-fill and re-heat. Slow but steady is the secret to having a long, hot bath in this house!
If I'm in a hurry then a shower is the name of the game, if I've got at least an hour spare then the bath is the way to go!