Black and grey water tanks show full when they are not, how do I fix this?

[JustinChase]

So even when empty the black shows full and the grey shows 3/4 full, which is not ideal.


I understand 'stuff' can build up on the sensors and cause this, but how does one fix that?


Is there a better system I can install or upgrade to which will give me good, reliable readings that isn't susceptible to this sort of thing? I'd like to know I can always rely on the readings and not have to 'remember' when they might be full.