Fuel filtration - location of primary inline filter

[GEM43]

Is it important that the primary filter is located close to the engine/secondary filtration? I ask because I’d like to fit an upgraded primary filtration arrangement (twin Racor with changeover valve) but it would need to be at least three pipe metres upstream from the secondary (fine) filter. Is that a problem?

 

[RunAgroundHard]

No it’s not important. Your primary will deal with the significant crud, plus water, then the clean fuel gets the fine filtering before entering the injection pump. 3cm to 3m separation makes no difference from a filtering objective. The only down side of long fuel lines from tank, to filter, to lift pump is an increase in friction losses that the lift pump has to overcome, but if the line length is broadly similar to what was there before, then no issue.

 

[Freebee]

fit it where you like it makes no difference, just make sure you can service the filters change elements -allow sufficient head room and can drain water without needing to become Houdini

 

[Oily Rag]

Just remember that if you locate it at a high spot, you will need to prime it. And any leaks will suck air rather than leak diesel.

 

[GEM43]

Just remember that if you locate it at a high spot, you will need to prime it. And any leaks will suck air rather than leak diesel.

Good points. I guess leaking diesel is preferable to sucking air but ideally neither woth good plumbing.

 

[bignick]

Remember that if you have a water drain in the bottom of the filter, that you want to be able to use, then the drain plug needs to be below the level of fluid in the tank, or it will draw air in when you open it

 

[Oily Rag]

My Racor is above the tank. I believe it has a non return valve preventing diesel flow back to the tank, but previous owner fitted isolation valves either side of Racor, so I close these before taking off the lid. Then I drain off (once every three years!) and top up with clean diesel.
There is never any visible water in the filter. I may be lucky because the filler cap is a female thread on a male upstand protruding from the deck.

 

[GEM43]

Remember that if you have a water drain in the bottom of the filter, that you want to be able to use, then the drain plug needs to be below the level of fluid in the tank, or it will draw air in when you open it

Interesting, I’ll ask whether there are non return valves in the filter to prevent this happening. Isolation valves either side of the filter would be a complete solution I guess.

 

[bignick]

Interesting, I’ll ask whether there are non return valves in the filter to prevent this happening. Isolation valves either side of the filter would be a complete solution I guess.

I have a quarter turn valve between the tank and the filter for that exact reason.
It’s much easier to not need to take the top off the filter and manually refill it from a jug though.
While It’s straightforward enough in a marina, I wouldn’t like to try to do it at sea.

 

[GEM43]

I have a quarter turn valve between the tank and the filter for that exact reason.
It’s much easier to not need to take the top off the filter and manually refill it from a jug though.
While It’s straightforward enough in a marina, I wouldn’t like to try to do it at sea.

The idea of having to do a filter change at sea is the catalyst for my planned upgrade. I have a CAV filter at present, it’s messy when the boat is still, at sea it would be horrendous.

 

[Fr J Hackett]

The idea of having to do a filter change at sea is the catalyst for my planned upgrade. I have a CAV filter at present, it’s messy when the boat is still, at sea it would be horrendous.

Horrendous or not it is something that you should not be afraid of or unable to do. There is a recent tread about a boat returning from Bermuda to Maine that sank and the skipper chose not to try and change fuel filters when they became blocked and the boat started to take on water, not related to the fuel problem but without the engine it complicated matters and eventually the boat was lost. Maybe an extreme example but changing a fuel filter should not be an impossible task, make it as easy as possible with the placement of filters and even use a duel filter set up to reduce the risk of having to do it.

 

[GEM43]

Horrendous or not it is something that you should not be afraid of or unable to do. There is a recent tread about a boat returning from Bermuda to Maine that sank and the skipper chose not to try and change fuel filters when they became blocked and the boat started to take on water, not related to the fuel problem but without the engine it complicated matters and eventually the boat was lost. Maybe an extreme example but changing a fuel filter should not be an impossible task, make it as easy as possible with the placement of filters and even use a duel filter set up to reduce the risk of having to do it.

Please read post #1