Fresh water level LED's

Hi Please can anyone help,
We have owned our 14 plate Kemerton for nearly a year nowand love it, up until now its been pretty trouble free.
However we went to the site at Crystal Palace weekend before last, I filled the fresh water tank before we left checking as I went and all the LED's on the panel correctly illuminated in turn as the tank filled through to full.
On arrival at site when we turned on the panel the low level alarm sounded and the tank only showed 1 red led, we continued to use water all weekend and I drained down and re-filled the tank on our return but we still have the same symptons, I have seen old post on the forum some people have used a fresh water tank cleaner which seems to clean any scale off the sensor rods and cure the problem.
Anyone actually tried it recently, if so were the results successful and which cleaner did you use, any help/advice gratefully received. 
Many thanks in Advance.
Arry.

Thanks for the link Paul I'll give the tank cleaner ago seems quite successful 

As I said in a previous post, I also tried the Elsan water cleaner method and it seemed to work immediately afterwards.  That was a several weeks ago.  This week I put cold water in the tank at home before going away for a few days and the gauge went haywire when it reached 75%  then reverted to zero.  
The following day it showed 75%  and has worked correctly while we've been away.
Don't be disappointed if it appears not to work at first. It's definitely worth trying.
The other thing to say, as others have, is that if the gauge fails, just estimate!