Water smell! Shureflow Pump Caravan

The caravan water system has been putting a smell into the water, I have sterilized the system with Milton but the smell soon returns.

I have had a good look over the pipe work and have hound a small particle filter on the inlet to the Sure Flow pump. In previous vans I have had a carbon filter as well (Carver pump) but no inline carbon filters on this system.

I have removed the particle filter and found small pieces of debris which has been sucked in over the years.  The filter separates easily into two parts so it can be cleaned.
The filter has now been cleaned and sterilized and smells very clean, hopefully the smell will now go.