Help, 3 brews failed

[Happy brewer]

after having bottle the Kilner beer a week ago, tried a bottle last night.. tastes ok, a little sweet, not much flavour, but no acidic or vinegar type tastes.
One thing I would like to know, can fermenting create smells like acidic etc, even when the beer is fine?
Also I am going to try on my next brew, which will be a Wilko's 2 tin real ale kit, I am going to try using 20-21 litres of water instead of the recommended 23 litres because I am thinking sometimes are the kits strong enough to make the whole 40 pints

[Hugh Jampton]

Put the heater into a bucket of water and stand the FV in the bucket. Putting the heater directly into the beer is a sure way of getting an infection.

[chris.laws.54943]

So.....you've had plenty of replies! Something I learned here is that the VWP cleaner and starsan (type) sanitizers do different jobs so still use both. But not fairy.

[f00b4r]

Also I am going to try on my next brew, which will be a Wilko's 2 tin real ale kit, I am going to try using 20-21 litres of water instead of the recommended 23 litres because I am thinking sometimes are the kits strong enough to make the whole 40 pints

It is not 23L that you should be adding to those kits, you should be making the combined fluids up to 23L or you may have issues with watering them down too much.
Also ensure you calibrate your fermentation vessel before hand using weighed water as the printed marks are notorious for being inaccurate (do not use a measuring jug to do this as they are often inaccurate as well and this will be exacerbated by using it multiple times to fill the fv; you can of course use one if you check it via weight first).