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Best filter for diesel bug /water.

Can you advise the best extra filter to fit before the standard fuel filter on my Nanni engine to remove water and the diesel bug from my fuel ?

Asked by: David Spencer  | 4.25pm, Friday 31 August

WW says:

It is best to fit a combined water-trap and fuel filter; this has a cartridge filter with a large aluminium container beneath. The filter will catch any bits and diesel bug growth, whilst the water trap below will trap any water being drawn from the tank.
It is however important to check the filter regularly, at least once a year; more often if diesel bug is suspected as it will clog the filter rapidly. Any water can be drained out of the trap using the plug on the bottom. It is worth mentioning that this plug must be metal not plastic, to meet the BSS requirements.

Rupert Smedley  | 6.10PM, Friday 31 August

I should think it will work OK as long as you drain the contaminants off regularly. After looking at their website I am not sure that the device has no plastic parts as there is no drawing or detailed photo. This would need to be checked, otherwise it will fail your next BSS examination, but if it is all metal it will be fine.

Rupert Smedley  | 10.43PM, Friday 31 August

To remove the diesl bug, you need to kill it firest, before trying to filter it out of the tank. Any filter will quickly become blocked if the microbial soup enters the system, no matter how good it is.
To do this, drain water regularly from the base of the tank, and use a chemical that precipitates out any further water (rather than emuslifying it- often poorly- to pass through the fuel). Then, if you have the bug, you can use a biocide (with care!) or, if you are so far lucky, then use a preventative treatment- for example, River Canal Rescue, who have had a lot of issues with the "bug" use Marine 16 and this works well, though there are many other avaiable.
one other thing you can do to avoid the bug, is to try and get as empty as you can with the tank, before refilling. A tank regularly topped up with contain fuel that degades as it is passed back to the tank hot from the engine. This not only changes the cetane rating of the fuel, but reduces the effectiveness, not only of th additives already in the fuel, but anything you add to the tank. Diesel fuel has a shelf life of about 12 months if kept below 15C. Fuel tanks in boats tend to be in the stern, whhere the effect of sunshine on the black paint causes them to heat up, while the engine often returns fuel at 50C and aobve. This means the proper life of the fuel in a narrowboat is around 6 months or less, before it starts becoming more prone to infection, as well as the quality of the fuel degrading seriosuly- often noticed if you have a diesel heating system fitted.

Mark Langley  | 9.31PM, Wednesday 5 September

Readers say:

I was thinking of fitting a MLS Fuel Purifiner, do you know if it would work well ?

David Spencer  | 8.13PM, Friday 31 August

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