Fuel filtration - how to make your own rig

[superheat6k]

I was recently asked how I made my fuel filtration rig.

I don't use additives and I don't expect to suffer fuel related breakdown. Instead I keep the fuel dry and clean - here's how ...

The set up is quite straightforward to understand.

On each system there are three connection points, each with a female instant connector.

1 Tank low point drain. On my boat these are hidden away at the aft end with large gate valve. Ive connected a copper 3/8" tube via adaptors and led this along side the engine adjacent to the fwd end, with a 3/8" ball valve to the female instant connector. The valve is clamped down.

2 Spill return line. I've fitted a 3/8" tee on the fuel return pipe from the fuel pump and injector spills, with a pipe running again to the fwd end of the engine - at deck head level. Another ball valve and instant female.

3 Fuel filter inlet pipe from tank. Another 3/8" tee ditto the spill line set up.

The rig itself is a Baldwin Fuel oil filter / coalescer with a Holley 12vdc fuel pump. The inlet passes first into the Baldwin filter and then on to the pump. Each of the inlet and outlets is on to a section of rubber fuel quality hose ending in the matching instant connector Males. It is important to filter first and pump second, because the pump smashes water drops into tiny particles which will pass through the coalescer filter.

I have a power supply that the filter plugs into nearby with a simple switch.

The rig can draw from either the fuel pickup or low point drain. It can discharge into either the spill return or the fuel filter inlet.

Being able to discharge into the fuel pickup line has several advantages ...

a. This partially pressurises the pickup line, which makes pre-filling fuel filters or priming the fuel system a doddle. Set it up and turn it on, then vent filters and bleed the system at you leisure.

b. If a slug of crud were to block the pick up then this effectively blows the crud back into the tank.

c. I can if necessary direct feed the engine, should the engine fuel lift pump fail.

Also it is possible to draw from one and flow to the other tank.

For routine polishing draw from the low point and return via the spill and simply leave it to circulator ~1-2 hours. A check of the fuel bowl on the filter shows any water or contaminate settled out at the bottom.

This is the list of parts - ~ £350 ...

Here is a kit of parts, but note I have found a cheaper filter and pump (not tested for this application) ...

Item	Make details	Model	Qty	Ebay	Price
Rack	Imagination		1
Filter assy	Racor 500 copy		1	393074412399	£24	£24
Filter element	Racor 500 copy		1 + Spare	283571129306	£7	£14
Filter adaptor	As required - might come with filter	to suit 3/8” hose	2			£0
Pump	Holley or similar		1	323267905619	£22	£22
Pump adaptor	to suit pump size > 3/8” compression		2			£0
Hose 3/8”	Suitable for diesel fuel		6m	265215557691	£4	£24
Dripless Instant connectors	https://www.flowfitonline.com/hydraulic-qrcs-and-adaptors/quick-release-couplings/hydraulic-flat-face-quick-release-couplings-set-12-bsp-dn08-iso-125-350-bar-rated-45-lmin	6		£20	£120
Hose adaptor	3/8” hose barb > 3/8” BSPP		2		£5	£10
Seal washer	Dowty type to suit 3/8” BSPP fitting		lots		£10	£10
Drain point adaptor	e.g. 1” BSPTM to 3/8” compression		2		£5	£10
Copper tube	measure what your boat uses 3/8” and 10mm are close but not the same		10m		£3	£30
Tee	3/8” > 3/8” > 3/8” compression	or 10mm	4		£6	£24
Ball valves	3/8" compression or extra fittings as necessary to allow it to fit to a 3/8” pipe	or 10mm	6		£6	£36
Cigarette plug & socket	Euro style is more positive or marine 2 pole type. Bulgin Buccaneer is the best make.		1 plug & socket		£10	£10
Switch	Can be on the cable		1		£5	£5
						£339

 

[Sandy]

b. If a slug of crud were to block the pick up then this effectively blows the crud back into the tank.

Sounds brilliant, but why blow the slug of crud back into the tank?

 

[prv]

Because if it fit up the pipe it wouldn’t be blocking it. The only place it can go is back out the way it came in.

Is the rig something you carry on board all the time, or just bring down to the boat when needed? If the former, why the quick-disconnects and carrying frame - wouldn’t it be cleaner and more convenient to have the polishing components plumbed in permanently?

Pete

 

[Sandy]

Because if it fit up the pipe it wouldn’t be blocking it. The only place it can go is back out the way it came in.

I'd want the crud captured somewhere, ideally the filter, rather than go back in the tank lurking to strike on a dark and stormy night.

 

[Moodysailor]

Great engineering, and agree with the approach - the best thing is clean fuel, not treated fuel.

 

[noelex]

If possible I would also recommend fitting a built in system. The most valuable time to polish is when the tank contents have been stirred up during sailing. If you have multiple tanks the polish system can also double up as a fuel transfer mechanism.

 

[prv]

I'd want the crud captured somewhere, ideally the filter, rather than go back in the tank lurking to strike on a dark and stormy night.

So would we all, but if it could reach the filter then that's where it would have been in the first place. If it got stuck in the end of the dip pipe then the only way it can move is back out the way it came. I had exactly this problem a couple of months ago. It took a good hard shove on the dinghy pump to force the plug of gunk back out the end of the tube. We had the inspection hatch open so were able to then scoop it out - ideally the OP's polishing system might have something like a larger-diameter dip pipe of its own to collect such detritus, but the first step has to be pushing the crud back out of the main pipe.

Pete

 

[Sandy]

So would we all, but if it could reach the filter then that's where it would have been in the first place. If it got stuck in the end of the dip pipe then the only way it can move is back out the way it came. I had exactly this problem a couple of months ago. It took a good hard shove on the dinghy pump to force the plug of gunk back out the end of the tube. We had the inspection hatch open so were able to then scoop it out - ideally the OP's polishing system might have something like a larger-diameter dip pipe of its own to collect such detritus, but the first step has to be pushing the crud back out of the main pipe.

The OP does not have an ideal solution and should go back to the design and engineer the problem out. Says retired engineer.

 

[thinwater]

The OP does not have an ideal solution and should go back to the design and engineer the problem out. Says retired engineer.

Then explain your solution. We're all (many of us) retired engineers. He didn't tell us enough about his drop tube to comment on that, and in fact, it may have just been a generic comment, not specific to his boat.

He mentioned that his system can draw from another location and discharge in two places.

 

[Oily Rag]

Do the quick-release couplings require internal pressure to seal?
If they were at the top of a siphon, with the fuel tank below, would they suck air in?
(Like the Hozelock fittings in my garden)

 

[Moodysailor]

In my view (also an engineer, sorry) the question/issue about larger pieces of debris that may clog a dip tube are why there should be access to the tank, IMO. A removable hatch large enough to get in and see inside, and extract anything too big to be drawn up is pretty basic stuff really, but many leisure boats don't have this (commercial do).

The job of the system proposed is to polish the fuel, to try and make it a debris removal system would require a different approach and level of engineering. Sorry for speaking on behalf of the OP, and apologies if I'm mistaken, but I believe this is not the intention of their design.

The nice aspect of someone sharing their design and ideas on a forum like this is that we can all share our own best practices, then make our own version of the ideal system for our use-case

 

[Sandy]

Then explain your solution. We're all (many of us) retired engineers. He didn't tell us enough about his drop tube to comment on that, and in fact, it may have just been a generic comment, not specific to his boat.

I don't recall saying I had developed a fuel polishing system?

This is what I do - I ensure that the fuel is clean:

• I don't use fuel from marinas as the turnover is low (I prefer buying my fuel from a filling/gas station as they will be using a road tanker every few days against one a month/year at the marina. It is more convenient to fill up on the way to the boat and my usage is low about 100l (26 US gallons) per year. I know this will not be feasible for a motor boat);
• I don't use 'red'/marked diesel due to low turn over (how long has the fuel been in the storage tank?);
• I buy enough fuel just for the voyage about to be undertaken (I don't subscribe to the 'keep your tank' full school of thinking);
• I ensure that the filler cap is secure, the 'O' ring in undamaged and well greased (A long time ago a naval architect thought it was a good idea to have a horizontal deck level filler! The mitigations instil confidence as the ocean passes over the cap at seven knots!);
• I filter the fuel before it goes into the tank (It does take time, but you will be amazed at the amount of 'crud' that captures);
• I have a Racor type primary filter that has a water separator and filter;
• A good secondary filter;
• The tank and fuel lines get cleaned every three years (the naval architect did make fuel tank extraction really easy); and
• The jerry cans get cleaned every year.

In this summer's 1450 nm cruise in everything from a F0 to F7, sea conditions from glassy smooth via a short chop though to a four meter breaking swell, I had no fuel issues.

Several years ago I caught a dose of the diesel bug from marked fuel purchased from a small marina, hence developing the above strategy. I am removing and cleaning the system this winter I'll try and remember to take some pictures of the condition of the filters.

Thinking back to when I worked full time we had a fuel polishing company visit annually to polish the fuel for the standby generators. Their lines were 10 times the diameter of the ones we were using to feed the engines. No chance of any crud blocking the fuel lines and being returned to the tank there!

 

[superheat6k]

I do not agree with having a fully plumbed system, because it lacks flexibility, and yes a piece of crud still in the tank isn't ideal, but best not jammed in the main pick up.

I can remove the instant connector on the pick up and simply dip the tube into the filler. I can also use it to bunker fuel from a drum, or indeed to a drum (or 2).

The instant connectors I have used are no longer findable on Ebay, but yes they are dripless self sealing. Screwed connections could be used, or I could return into the filler, but for me having the flexibility was the ideal.

I do carry the rig on board, and routinely plug it in for an hour or so on each tank to polish the fuel about every 2-3 months, and always after fueling. This task is its main purpose.

This idea might not suit many, but for me it works and having been asked specifically for details I thought why not share here. I am surprised how some find room to criticise, after all this forum is for Practical Boat Owners.

 

[pvb]

So would we all, but if it could reach the filter then that's where it would have been in the first place. If it got stuck in the end of the dip pipe then the only way it can move is back out the way it came. I had exactly this problem a couple of months ago. It took a good hard shove on the dinghy pump to force the plug of gunk back out the end of the tube. We had the inspection hatch open so were able to then scoop it out - ideally the OP's polishing system might have something like a larger-diameter dip pipe of its own to collect such detritus, but the first step has to be pushing the crud back out of the main pipe.

The standard Volvo Penta pickup pipe has a fairly large metal gauze filter surrounding the open end - a good solution.

 

[thinwater]

I don't recall saying I had developed a fuel polishing system?

This is what I do - I ensure that the fuel is clean:

• I don't use fuel from marinas as the turnover is low (I prefer buying my fuel from a filling/gas station as they will be using a road tanker every few days against one a month/year at the marina. It is more convenient to fill up on the way to the boat and my usage is low about 100l (26 US gallons) per year. I know this will not be feasible for a motor boat);
• I don't use 'red'/marked diesel due to low turn over (how long has the fuel been in the storage tank?);
• I buy enough fuel just for the voyage about to be undertaken (I don't subscribe to the 'keep your tank' full school of thinking);
• I ensure that the filler cap is secure, the 'O' ring in undamaged and well greased (A long time ago a naval architect thought it was a good idea to have a horizontal deck level filler! The mitigations instil confidence as the ocean passes over the cap at seven knots!);
• I filter the fuel before it goes into the tank (It does take time, but you will be amazed at the amount of 'crud' that captures);
• I have a Racor type primary filter that has a water separator and filter;
• A good secondary filter;
• The tank and fuel lines get cleaned every three years (the naval architect did make fuel tank extraction really easy); and
• The jerry cans get cleaned every year.

In this summer's 1450 nm cruise in everything from a F0 to F7, sea conditions from glassy smooth via a short chop though to a four meter breaking swell, I had no fuel issues.

Several years ago I caught a dose of the diesel bug from marked fuel purchased from a small marina, hence developing the above strategy. I am removing and cleaning the system this winter I'll try and remember to take some pictures of the condition of the filters.

Thinking back to when I worked full time we had a fuel polishing company visit annually to polish the fuel for the standby generators. Their lines were 10 times the diameter of the ones we were using to feed the engines. No chance of any crud blocking the fuel lines and being returned to the tank there!

So your response perhaps suggests he should replace the existing fuel pick-up line with a larger one with no strainer on the end, and perhaps place a strainer at the top where is is accessible (before reducing the line size). I have done this in boiler systems. I never liked pipe-end strainers in the tank. You can't clean them easily.

In gasoline systems a common culprit is the anti-siphon valve.

 

[NormanS]

A properly designed fuel tank with a dirt sump with a regularly used drain valve, means that I don't need to go through all that performance. Any water or dirt automatically drops into the sump. The system works 24/7.

 

[Falcoron]

A properly designed fuel tank with a dirt sump with a regularly used drain valve, means that I don't need to go through all that performance. Any water or dirt automatically drops into the sump. The system works 24/7.

That is the ideal way of course, but I've yet to see this on a boat.
Boat builders don't usually give a toss how easy or difficult things are to get at or work on.

Polishing the fuel with a simple pump and good filter seems a good way to remove any crap or water and is what I'm going to do on mine as i refit tanks, filters and fuel lines.

 

[The Q]

I built my own external cleaner, that I plug in when every I'm down at the boat not going anywhere,
it's all built onto a plywood stand..
long copper pipe to drop into tank.
rubber pipe to
copper pipe that goes into the bottom of the Demijohn through the bung,
shorter copper pipe that picks up diesel from half way up demijohn..
rubber tube to diesel lift pump ,
rubber tube to standard diesel filter (same type as fitted to the boat).
rubber tube to a shorter copper tube that dumps fuel back into tank..
the pump runs of a car battery charger..
whole lot cost less than £50..

it took a lot of water out the first time and black gunge which settles in the demijohn, when the demi john fills with water, I pour it off into old 2 litre milk bottles for disposal later..

No drain at bottom of the tank which is almost impossible to get at anyway.

Note about the filters, I thought they were expensive from the boat yard.. After a bit of research I found the same filter was used on a tractor, So I bought a pack of 10 filters from an agricultural suppliers... For about the same price as one filter from a boat yard...

 

[iamtjc]

I built myself a simple pump & racor style filter mounted on a piece of board to do periodic cleaning of the fuel. Nothing different to what others have done. I used one of those rubbery baskets to transport it and keep all the tubing neat.

https://www.plasticboxshop.co.uk/images/large-flexi-bag-p3741-15543_image.jpg
Turned out to be brilliant if I run the thing in the basket as it catches all the drips and keeps everything clean and tidy.

 

[roaringgirl]

I put a T valve into the fuel feed just downstream of the Racor, and ran a line via a small electric facom fuel pump to another T-valve going into the fuel return, just before the tank.

When the engine's not running, I can twist both the T-valves and run the electric pump to pull the whole tank through the Racor over a couple of hours.