Smell from toilet bowl and water hammer - what to do?

Hi there

I recently had to have the inlet valve for my toilet replaced as it was spraying everywhere and this ended up with a leak through the ceiling! Before it was replaced i also noticed that the ballcock arm was pretty much at the top and hence the cistern was full to the brim with water.

I now have a new inlet valve and the ballcock has been adjusted so that the water level is about 1 cm below the line marked on the cistern. Since this has been done though I now have 2 problems:

1) There is sometimes a foul smell coming from the toilet bowl - it is not there all the time. As our bathroom is in the middle of the house we have a long run of horizontal soil pipe running under the floor boards of the next room before dropping vertically into the drain. I am thinking that there is now less water going down the pipe with each toilet flush and therefore not everything is going down the soil pipe so it ends up sitting in the pipe. Would adjusting the ball cock result in a bigger flush? This problem has only occurred since the valve was changed and the cistern has a lower water level.

2) After the inlet valve was fitted I ended up with water hammer on turning off taps, using washing machine etc. Initially I managed to get rid of this by turning off the water supply and draining the highest and lowest point taps. This worked for about a week but the water hammer is now back although the banging noise is not as loud as the first time. Any suggestions on what to do - do I just repeat the process?

Thanks in advance for any help - apologies for the long post but I am not that good at explaining myself!

Yes adjusting the level of the ballcock will result in a bigger flush (although its current standard to limit it to 6litres, but who cares!) Try it and see.

The water hammer is surprising, unless it was there before the original system was not malfunctioning. This could be caused through pipe falling off clips (or insufficient pipe clips), change in water pressure (possible, if this actually caused the original failure of the ballcock and isolator, in which case try turning down the mains stopcock a little), amongst other things. It's a starting point anyway.

I doubt the 1cm would make a jot of difference.
Easy to alter though.
I wonder if you're smelling the dampened material under the loo, which would have been sprayed for years if ther have been wee boys in the house.

What sort of water hammer?
The pressure might have been released by the old, leaking ball valve washer!