Water in Diesel Tank - feedback after tackiling it - any better ideas ??

[Halo]

My boat is now 8 years old and I thought it was time to see if there is any water in the tank bottom. There is no drain fitted which I think is rubbish design so here is where I have got to.
Firstly I shone a bright light on the side of the plastic tank to see if I could see anything through the tank wall - I could not
Secondly I bought some "water worms". A number of outlets including ASAP seem to sell similar items - they are like a sock with some compound in them which absorbs water. You put them in the tank and they soak up the water. Unfortunately they all seem to be 1 1/2" diameter so even if I can get them into the tank they may not come out again when expanded. To tackle this I got SWMBO to use her sewing machine to modify a Water Worm to make it max 1" diameter and I took out enough of the compound to cope with the reduced volume. I put this into the tank but nothing happened which seemed re-assuring but I was not happy to leave it at that.
I then got a Pela pump and tried to put it to the bottom of the tank to suck up any water. I used the filler hole as access but it is angled so the draw pipe hit the side of the tank and I was not sure I was right at the bottom. I tried sucking but no water. I then weighted the end of the draw pipe with stainless nuts and I could tell it was on the bottom. I managed to suck out about a mug full of black crappy liquid with the diesel. I concluded there is probably just a small amount of water at the bottom which I will have to live with and I will draw it out again once per season.
I always dose with Grotamar when filling up so perhaps some of the black **** was that !
Have I missed a trick - anyone ??
Martin

 

[pmagowan]

Fitting an access hatch!

 

[Ian_Edwards]

You could try building a fuel polisher, a simple small electric pump, a fuel filter/water separator with a glass bowl, some plastic tubing and a short length of copper pipe.

Rig it up so that the fuel is drawn through the copper pipe, which you place at the bottom of the tank, through the pump and then the filter/water separator (a 10 micro filter should do) and then back into the tank.

If you rummage around in the bottom of the tank with the copper tube, you should be able to extract any water and gunk, the water should show in the separator bowl and the filter will take the gunk out of the fuel.

 

[jwilson]

Fitting an access hatch!

Not easy on thin walled plastic tanks - I had nearly 2 years of intermittent diesel leaks (ranging from major to minor) before I finally managed to seal the access hatch I'd fitted for the same purpose in a plastic tank in a Jeanneau. Three different hatches in an expanding hole before I manged to seal it properly. Also a variety of gaskets/sealants.

After about 8 years from new I extracted maybe a pint of black water from the bottom, though nothing like that had ever made its way to the primary or secondary fuel filter. The takeoff was high enough up and away from the low point of the tank to keep the water inside.

Now I've got the access hatch Mk III sealed I'm very reluctant indeed to touch it again for several more years - which rather defeats the object of having a hatch.

 

[lw395]

I reckon 'hoovering' with a pela once a season or if any water is seen in the separator bowl keeps things under control. Heeling the boat so the pela has best chance of finding water.
There will always be a bit of water, the name of the game is to keep the amount small, so you can be sure there is not enough gunge to ever block the filters.

 

[NormanS]

I don't want to sound smug, but life is soooo much simpler with a sump and drain. The modern trend towards shallow, broad tanks defies common sense.

 

[pmagowan]

I don't want to sound smug, but life is soooo much simpler with a sump and drain. The modern trend towards shallow, broad tanks defies common sense.

Unfortunately my plans for tanks in my new boat would put them mostly too low for a drain so I will have to make do with an inspection hatch. I will, however, be having an inbuilt fuel polishing system which should remove any water

 

[vyv_cox]

I reckon 'hoovering' with a pela once a season or if any water is seen in the separator bowl keeps things under control. Heeling the boat so the pela has best chance of finding water.
There will always be a bit of water, the name of the game is to keep the amount small, so you can be sure there is not enough gunge to ever block the filters.

+1. If you don't have a sump this has to be the best way.

My tank has no sump as built but the bottom fuel take-off has a 25 mm upstand. Water can accumulate below that unless drained off by another fitting that is flush with the bottom of the tank. I had never drained it but this year I noticed some fuel dripping from the drain plug. I tightened it a little and stopped the leak. A few weeks later I took the tank out to replace a failed sender unit and looked at the drain plug at the same time. The brass plug threads against the stainless steel boss had corroded galvanically, leaving the plug literally holding by a thread. When I tightened the plug another half turn it fell out, the threads now being non-existent. I was very fortunate not to have dumped a full 100 litres of diesel into the boat. In future I will use the Pela method, which has to be preferable to removing the new plug to drain off 100 ml or so.

 

[lw395]

Unfortunately my plans for tanks in my new boat would put them mostly too low for a drain so I will have to make do with an inspection hatch. I will, however, be having an inbuilt fuel polishing system which should remove any water

I think, if I were specifying a new tank, I would at least have a permanent standpipe to the lowest point of the tank for sucking out water.

One of my other concerns would be avoiding the situation with many yacht tanks, where you need 'several' (going on 'many') litres of fuel in the tank to be sure of not sucking air in a bit of chop.
That's actually the only thing that's ever caused a yacht engine to cough on me at an embarrassing time.

 

[pmagowan]

I think, if I were specifying a new tank, I would at least have a permanent standpipe to the lowest point of the tank for sucking out water.

One of my other concerns would be avoiding the situation with many yacht tanks, where you need 'several' (going on 'many') litres of fuel in the tank to be sure of not sucking air in a bit of chop.
That's actually the only thing that's ever caused a yacht engine to cough on me at an embarrassing time.

These problems should be resolved in my system by having a raised 'day tabnk' with a gravity feed to the engine. The main tanks will simply be stores and will pump the fuel to the day tank for use, through a water and particulate filter.

 

[Halo]

I reckon 'hoovering' with a pela once a season or if any water is seen in the separator bowl keeps things under control. Heeling the boat so the pela has best chance of finding water.

Good point about heeling her - I did miss a trick!

 

[NormanS]

These problems should be resolved in my system by having a raised 'day tabnk' with a gravity feed to the engine. The main tanks will simply be stores and will pump the fuel to the day tank for use, through a water and particulate filter.

Ah well, if you're going to have a day tank, there's nothing to stop you having a sump and drain on it.

 

[pmagowan]

Ah well, if you're going to have a day tank, there's nothing to stop you having a sump and drain on it.

Yes, I can on that tank but since only prefiltered fuel can enter the day tank it won't really be as important.

 

[macd]

I don't want to sound smug, but life is soooo much simpler with a sump and drain. The modern trend towards shallow, broad tanks defies common sense.

Worse still, it defies good practice.*
The answer for people such as pmagowan, who have insufficient room below the tank, lies in lw395's suggestion of a permanent standpipe, i.e. a pipe which reaches the lowest point of the tank but exits from the top of the tank. This also largely precludes vyv's near miss with an external fitting failing and flooding the bilge with diesel.

* Which in this respect is almost completely absent from the new boat market. If RCD is to have any credibility, why does it not address such issues? Oh, did someone mention brass skin fittings...?

 

[Stork_III]

I think, if I were specifying a new tank, I would at least have a permanent standpipe to the lowest point of the tank for sucking out water.

Standard fitment on my HR. Normal fuel take off point stops short of tank base. An additional take off point, with removable external pipe, is provided for tank draining

 

[pyrojames]

If you are fitting a new tank, then I'd strongly recommend fitting a small sump and a horizontal take off with a ball valve. You then don't need to get under the tank to drain it. You can fit the main pick up an inch short of the bottom of the sump. Drain off the bottom of the tank very month, to check for water, pour any diesel off the top back into the tank.

 

[NormanS]

If you are fitting a new tank, then I'd strongly recommend fitting a small sump and a horizontal take off with a ball valve. You then don't need to get under the tank to drain it. You can fit the main pick up an inch short of the bottom of the sump. Drain off the bottom of the tank very month, to check for water, pour any diesel off the top back into the tank.

That's what my tanks have, except that the main pick-up is an inch above the bottom of the tank.