What type of valve is needed?

You must ensure the valve (and whatever else you install) has protection against being stepped on, dropped on or otherwise smacked. Because a cracked nipple, elbo or fitting can allow an unintended fuel spill. It's bad enough with the spill. But even worse if you were out in heavy weather and something fell on it and you lost the fuel underway.

After all the discussion an advice, I guess my question is "why bother??" Have you had such bad experiences with your fuel quality? My experience was that after several thousand gallons, I drained my tanks to do some plumbing and no water or crud came out. Perhaps you could do as I did; I simply let both my tanks empty to below half volume, then pumped from one tank to the other to drained that tank, then reversed the process to drain the other tank.

Or, you might want to consider going one step further, and convert those two nice low drains into being your fuel supply lines, link them so they always self level, and then as long as you keep an eye on the filters, no crud or water can ever build up in the tanks, because it's the bottom they drain from, so sort of fuel polishing continuously. Mine are set up like that, and it works well. Not for nothing Nordhavn use this approach.

That would obviate any slight leak risk and make a gate valve probably ok. I have never liked the system of fuel pick up tubes, which always end well above the bottom, so crud can build up, just to be nicely stirred up by a seaway in time to block your filters at a time you least want them to be. Just a thought..?

Peter that does turn your fuel system into a fuel polishing system.

I use a small pump (oil changing), some fuel hoses and a 1/8" copper tube to pump up fuel occasionally off the bottom of the tanks. Copper tube so I can bend it so it can be snaked down to the lowest parts of the tank. I remove the water and bits of crud that way and thus inspect the tank and fuel. I try to do this every several months. I get more "crud" than water.

I've had to do this because the fuel tanks wer'nt built to my specifications. However I like the peace of mind the pumping gives me.

Peter B said:

Or, you might want to consider going one step further, and convert those two nice low drains into being your fuel supply lines, link them so they always self level, and then as long as you keep an eye on the filters, no crud or water can ever build up in the tanks, because it's the bottom they drain from, so sort of fuel polishing continuously...

Click to expand...

A couple of observations:
1. I`ve read on TF that Lehmans don`t draw and return as much excess fuel as some others, thus reducing the polishing effect.
2.Not picking up from the very bottom of the tank creates a kind of "quasi sump"(in place of the real one Nigel Calder recommends), ensuring crud and water are not picked up. The ability to drain combines crud drainage with pick up above the tank bottom where any remaining crud lives.
3.Cappy 208 raised the danger of stepping on the valve. The IG tank drain location makes that very unlikely. Interestingly, the fuel tanks on my IG are located aft of, NOT beside, the engines, the standard side water tanks occupy that position.

Given that dirty fuel is the most likely show stopper for a diesel I wanted to ensure I always had clean fuel. I had to replace tanks, so went for a day tank set-up.

I have 4 tanks with deck fills, total capacity 4000 litres. The day tanks total 700 litres and can only be filled via the fuel polisher. I run the engines only from the day tanks, and keep them full when at the dock. Each engine supply is via a twin RACOR, so easy to switch over in the event of a blocked filter as well.

The 4 main tanks have engine supply pickups that are 1/2" or so off the bottom, but I don't use these anyway. The polisher pickup tubes however go down almost touching the tank bottom. The intent was the polisher will get any water/crud that is in the tanks.

I'm now at a bit over 17,000 litres consumed with this setup, and have never changed the filter on the fuel polisher, and its gauge is telling me it has very little crud in it. I have only used fuel purchased in USA, Canada or Australia. All obviously clean. The system was designed in case of the need to fuel from drums or suspect suppliers in remote locations/developing countries etc.

Should the polisher fail then engine supply/return can use any of the main tanks via the fuel manifold configuration. And there are also tank inter-connectors at the bottom, with ball valves, that could be used to drain a tank if needed, eg should some idiot put a water hose into the wrong deckfill. The system is working quite well.

First pic shows the interconnector or the aft tanks, which I normally leave open to self level. Then pic of the polisher and its supply/return manifold. Then engine supply and return pics.

Brian, that set-up looks soooo beautiful compared to mine it almost makes me want to weep - but I won't...because my set-up is so cheep...

Erm ! I think I mentioned PTFE (plumbers tape) in an earlier post.
Most of the fittings have a tapered thread, the more you tighten the more they seal.


Insequent, Beautifully set up, a real credit to you.


I'm afraid I'm in the same camp as Peter B, fuel sump drain, engine pre filter, simple and cheap as chips.

Brian,what a stunning example of onboard technology. It would not look out of place in a laboratory.

Thanks Peter, IR & Bruce. Credit is due to the Port Townsend Shipwright's Co-Operative team, lead by Todd Lee and Chris Brignoli in my case. I just paid the bills, although that was not an insignificant task in itself. The guys all did a fabulous job of a very comprehensive systems refit.

One day I might upgrade some of the cosmetic aspects of the boat, head decor comes to mind in particular. They are still pretty much "1980's chic". But livable after I removed 2 layers of wallpaper to reveal white lamipanel.

That sure is nice, Brian. I'm salivating.

I replaced my fuel lines when I replaced the tanks. I couldn't decide whether to draw from top or bottom of the tanks so I went with a modest manifold that allows either option.
The bottom drain points are tied together, with a tee to the fuel filters, and another tee and valve to a sight glass shared by both tanks.
It works much better than it looks.

My vessel (1999) had 3 ports at the bottom of each fuel tank for engine feeds, tank crossover, and sight level tubes. All had shut-off valves at the tank. My questions is, I had heard that newer vessels were required to have no ports at the bottom to eliminate tank leakage risk. Not sure if this is correct or not??