Saint Jean de Losne: Reconfiguring Wanderlust’s Fuel Vents

Wanderlust comes out of the water for work in 2018.

Note: I’ve been slow in following up with the posts on Wanderlust’s story. The 2018 season was lost in entirety to the remedial works that only became possible after the dispute with the builder was settled on February 6. As of 2019 Wanderlust is better than she ever was, though we are still dealing with several issues.

If you’d like to catch up on Wanderlust’s history the posts concerning the problems and dispute have been categorized under “The Troubles”. The link should get you most of the story, at least the portions that have been written up, in typical blog-style reverse chronological order.

Without further adieu, to the resolution of a major problem: Fuel tank venting and blowback…

Wanderlust’s tanks under construction: The black tank is in the foreground, the red diesel tank is in the middle near the worker, and the white tank is in the distance near the stern.

Wanderlust is configured with two tanks to take advantage of the significantly lower tax on the red-dyed fuel used for heating and electrical power generation. The red diesel tank is a dedicated fuel supply for the generator, boiler, and heating stove while the white tank provides un-dyed fully taxed “road” diesel to the main propulsion engine. It is a configuration set with Continental cruising in mind.

The build contract lists Wanderlust’s red and white diesel fuel tank capacities at 1200-liters; the official documentation after launch reflected those numbers. Years later we learned that the usable capacity of the tanks had been substantially over-represented; both reservoirs held significantly less usable fuel than specified. Nevertheless our rate of fuel consumption after launch was low; the fuel added to Wanderlust’s tanks at the plant during the build was sufficient to last us more than a year.

It was only as we prepared to cross the English Channel that we considered filling the tanks for the first time. Assuming Wanderlust’s fuel levels were being displayed properly on the gauges, there should have been enough fuel on board to make the Channel crossing from London to Calais France. Nevertheless, it’s generally advised to fill the tanks in advance of this sea crossing for various reasons. With the need to add fuel on the Thames there came a challenge: Buying white diesel.

Wanderlust fuel tank being filled at the plant. We were told later that the fill rate was 50L/minute and that there was no blowback.

Fuel blowback caused by filling at 23 L/min in St. Mammes.  Regulations specify testing for blowback at 30 L/minute.

On the Thames it is difficult to buy diesel without red dye in it. Generally boaters purchase red diesel and pay tax based on its claimed use. Often red diesel is purchased with a 60:40 propulsion to domestic tax split, reflecting a “typical” percentage use. Under this system there is no need for separate red and white diesel tanks. As a result many boats have just a single fuel tank, which they fill with red diesel. Consequentially there was no motivation for the boatyards to sell fully taxed white diesel.

As we contemplated fueling up before crossing the Channel to France, the Thames fuel situation left us with a dilemma. If we added red diesel to our white propulsion fuel tank we risked scrutiny if inspected on the Continent. The pink tint in the fuel would be a red flag to the authorities looking for a sign that we were wrongfully using the lower taxed domestic and commercial diesel for propulsion. We could make our case by presenting receipts showing the red fuel in the propulsion tank was properly purchased with tax in the UK. Nevertheless it could be a time consuming and uncomfortable complication. It was a situation we preferred to avoid. The presence of red dye in the propulsion diesel tank would not go away quickly; it would take years for the detectable levels of red in the white fuel to be diluted away. Why bother having separate red and a white tanks if you are going to set yourself up for a potential problem later?

The fuel tank vent cap showing paint

Wanderlust in position for the tanker delivery at Penton Hook Marina.

Thus we decided to make the effort to add white fuel to the propulsion tank at the time of our first fueling. This turned out to be complicated to execute on a waterway where boatyards only want to sell red diesel.

Eventually we found a solution. After some searching we found a tanker delivery company that would bring both red and white diesel by truck to Wanderlust at the Penton Hook Marina. The tanker would deliver to the bank overlooking the marina if we agreed to take on more than 1000L of fuel.

Could Wanderlust take on 1000L of fuel?

Assuming a linear drop on the fuel level displays I did the calculations. The receipts provided by the builder indicated that 1000 L of fuel was added to each of the two tanks in the plant. In both cases the tank level indicators indicated full at launch. At the time we ordered fuel for delivery at Penton Hook the gauges read between one quarter and one third full. From this I figured that it would take around 1400 L of a combination of red and white diesel.

A fuel tank inspection port

The fuel locker: The pencil is showing the drain slot near the fuel filling point that is marked with a red dot to indicate red diesel.  Fuel blows back from the fueling port and drains through the slot directly to the water.

The morning of the tanker delivery we moved Wanderlust amongst some old boats in a place accessible from the bank. When the tanker arrived the driver rolled out the fuel hose over the decks of the moored boats and started the fuel fill. Immediately there was confusion. The red fuel being added was causing the level indicator for the white fuel tank to rise. For a moment we thought that the filler ports had been mismarked, as they had come from the plant unlabeled and dabs of colored paint were added later. It seemed like a disaster. After our effort to find white fuel, was red fuel going into the white fuel tank?

Fortunately that was not the case.

After some inspection and a call to the builder we discovered a more benign cause: The fuel tank level displays had been mislabeled. It shouldn’t have been a big surprise, as the level displays, like the fill points, were not labeled at launch and had also been marked later. What we thought was the white tank level display really was showing the amount of fuel in the red tank. Thankfully the fuel was going into the correct tank after all. (Wanderlust is not the only boat where the fuel tank levels have been confused!)

The fuel tank gauge’s sender inside the tank. It sits about 70 mm from the bottom of the tank, roughly the same height as the fuel pick-ups.

The white fuel pick-ups with a 2 Euro coin showing the height above the bottom of the tank.

The tanker driver paused the fill while we sorted out the display issue. Once this mystery was resolved the pumping continued.

An unexpectedly short time after the fill was restarted, the tanker pump automatically shut off as fuel came up out of the filling point. Several seconds later a much larger foot-high fountain of foamy diesel spewed back out of the deck filler. After seeing the diesel mess I headed below to look at the level display. I was expecting to see that the tank was reading full.

To my surprise the display indicated that the red tank was only around 60% full. If the gauge scaled accurately, the tank wasn’t even close to full.

I asked the driver to try to add more fuel going slow. It didn’t work: Once again there was an automatic shut off followed by more fuel ejected out of the port into the pool of diesel inside the small locker near the wheelhouse door. No matter what the fuel level was reading, the tank was effectively full. In the end we took on 469 L of red diesel, well less than what I had calculated. At the end tank level display settled to 65% based on the 1000 L added before launch.

Access cut through Wanderlust’s hull during the summer of 2018 to repair the leaking welds.

When the white propulsion diesel tank was filled the same thing occurred, although at 90% indicated on the display at the end rather than 65%. Fuel was once again ejected from the filling port. Though the diesel fountain from the white fill wasn’t as vigorous as for the red tank fill, it still made a mess.

In the end Wanderlust took on only about 60% of the fuel that we told the tanker company that we would purchase.

Past the smaller than expected delivery the driver was clearly annoyed by the fuel spewing back out of the fill port, and for good reason. We learned later that the rapid expulsion of fuel from the filling port is called blowback. By law boats are to be designed so that this does not happen as it creates safety and environmental issues. Undoubtedly the tanker driver knew that Wanderlust’s fueling arrangement was not proper. But at the time we did not know.

The tanker company could have insisted that we pay for the amount of fuel ordered but they only asked to be paid for what they could deliver. With that I suspect they will never deliver to Wanderlust again under any circumstances.

After the tanker departed we pulled Wanderlust’s ropes and slowly left our position between the old barges. As we moved out we noticed a slick of diesel fuel on the water. It seemed that the old barges near Wanderlust were leaking a lot of diesel.

Wanderlust’s bottom stitched up and painted after her surgery.

Wanderlust on the hard in Saint Jean de Losne

“Polluting old boats,” I muttered to myself. “Somebody should do something about that.”

As Wanderlust left the port and turned downstream towards London I tried to understand what had happened. During the fill, in part because of the level indicator confusion, we had been in contact with the builder. When I asked about only being able to fill to 65% full there was no immediate comment.*

After another communication with the builder it was suggested that the fuel tank vents were closed. Tank vents? That was news to me. I had not seen or been told of any vents for the tanks. I started searching.

Eventually I discovered Wanderlust’s tank vents. These were both tucked back under the deck in the back of fuel locker near the fill points. To inspect the vents I had to put my head on the deck and shine a light to the back into the locker. Making it even more difficult, the vent openings were covered over with the black paint used to coat the inside the locker. It seemed to me that the vents might have been sealed by paint.

On seeing the condition of the vents I was confident that the fueling issues we had experienced were merely a consequence of sloppy paintwork. I figured that once the vents were opened wide, the next fuel fill would be issue-free. But that was wrong.

Hoses connect Wanderlust’s mild steel vent and fill pipes to the deck fittings.

Inside the engine compartment the fill and vent lines turn upward towards the deck. The smaller diameter white tank vent sits below the level of the wider fill pipe, making blowback inevitable.  The hole in the hull is for access to close a leak in the fill pipe.

After the Channel crossing, before we departed Calais France, we took advantage of the dockside pump to top up the tanks. Unlike the tanker delivery, we could operate this pump ourselves and could control the rate of filling. With the vents clear and as wide open as they could get, I crept the fuel in as slow as I could, much slower than the full bore delivery from the tanker.

It didn’t help; the result was the same. The fuel blew out of the fueling ports, just as had happened at Penton Hook. I could also now see that fuel was coming out of the vents also. In the end the tanks levels ended at the same level as they had been in Penton Hook. For reasons unknown to us, Wanderlust’s fuel tanks would not fill.

As at Penton Hook, there was diesel in the water around the boat in Calais. I looked around the harbor as we left trying to identify the offending boat.

“Damn old boats,” I grumbled as we moved out of the port.

After leaving Calais we contacted the builder by email about several problems, including the fueling issue. There was no immediate response about the fueling issue, though other problems mentioned in the message were addressed.

The hole on the upper left is the white diesel fill pipe entering the tank. On the left, blanked off, is the smaller vent line. The seams were re-welded in 2018 to fix the tank leaks.

Wanderlust in the grit blast shed after the tank repairs.

Wanderlust’s fueling problems continued despite our attempts to further slow the pump delivery rate and pausing frequently imaging that it would let the fuel settle into the tank.

The next response back from the builder came with a suggestion that we should fill the water tank at the bow before filling the fuel tanks. This is not something that we had to test, as the water tank was always completely full or very near full every time when we added fuel.

Nevertheless the suggestion did tell us that the builder realized that Wanderlust’s fuel tank venting arrangements were likely ineffective. The apparent purpose of adding weight at the bow by filling the 2000 L water tank was to increase the “upward” slope of the near horizontal under floor diesel tank vent pipes as they headed sternward. It figured that if the vents were more likely to drain to the tank they would be less likely to plug with fuel and more likely to function properly. Though filling the freshwater tank did not reduce the blowback, the suggestion to add freshwater did help us understand why the tanks’ vents were ineffective.

The diesel tank venting issue must not have been a surprise to the builder. Wanderlust’s tank vent lines come off of the top corner sides of the tanks and run near horizontal below the floor before they turn up to the deck in the engine compartment. The red tank’s vent pipes are the worst. They run six meters just below the steel joists for the level floor. It is hard to conceive that this configuration had any chance of working even if the builder managed to carefully keep the vent line sloping upwards, which he did not. At best, the vent pipe was always going to be near level. Indeed, once we had access to the bilge we could see later that the vent pipe actually drained away from the tank with around a 2% slope, making certain that it would become choked by the foaming fuel during a tank fill.

The new vent for the white tank

Red diesel being added to Wanderlust during a test of an alternative vent arrangement.

The white tank’s vent configuration is a little better. Just as with the red tank, the vent pipe parallels the fill pipe, with both coming horizontally off the top of the side of the stern end of the fuel tank and running about a meter into the engine compartment before turning 90 degrees up to the deck. Unlike the red diesel vent, this vent does appear to slope gradually upward. The arrangement might have actually worked except for one fatal flaw: The vent pipe runs below the height of fill pipe.

At the end of a fuel filling, when the white tank nears full, diesel necessarily backs into both the fill and vent pipes. Since the vent pipe runs below the level of the fill pipe it is the first of the two to fill with fuel. And when the vent blocks with diesel during a fill the air displaced by the incoming fuel can no longer escape. Blowback is inevitable. Though the original red vent configuration is hopelessly optimistic, the white tank vent never had a chance of working properly. Mounting a horizontal vent pipe below the level of the fill pipe was an obvious mistake by a builder who had to be aware that many of the boats he produced had fuel tank venting issues.

In the fall of 2015 we made an additional discovery that shocked us: The diesel fuel in the water that we had been seeing during fills was coming from Wanderlust. It wasn’t the old boats near the pumps at all. The oil slick was coming from our brand new boat.

What we hadn’t realized until then was that there was a drain to the water installed in the fuel locker two inches from the red diesel fueling port. In the light the slot around a drainpipe at the bottom of the locker looked like a weld. It was only when examined closely that we could see that there was a gap around the locker rim drainpipe designed to allow fluids in the locker to drain to the water. Each time we filled the diesel tanks multiple liters of fuel were expelled from the filling port. This diesel pooled into the locker and drained out into the water through the gap.

Diesel spills out of the tank locker’s drain and goes directly into the water.

It had become clear that we could no longer ignore Wanderlust’s blowback issues. We needed to do something.

Our next appeal to the builder resulted in a reply that was less than helpful: He would visit Wanderlust in France, but not to make repairs. Instead he would come with “a representative of our notified body to give a report on the alleged non-compliance of regulation.” Mind you that we had already forwarded graphic pictures of the blowback issue; there really couldn’t be much doubt that there was a problem.**

(There’s more on the role of building standards and how they relate to the construction of Wanderlust here. It is our understanding that members of the notified body don’t make the sort of visit being proposed by the builder.)

Per the builder’s email, to have Wanderlust evaluated to see whether her leaking fuel tanks and her obvious tank venting issues conformed to the Recreational Craft Directives would cost us a mere £3130, including time and travel. The sum was payable to the builder in advance. Otherwise the builder and the member of the notified body would not attend. There was no mention of reimbursement when our complaints were proven to be valid. Nor was there any assurance that the builder would resolve any problems documented during the inspection. We were asked to pay a considerable amount of money to prove something that we already knew was true.

This email message from the builder set the stage for the legal dispute.  In response we offered to return Wanderlust to the builder’s plant for inspections and repairs.  Our offer was not accepted.

To us the builder’s proposal served only as an inflammatory bluff. There was no productive purpose. It did not bring us closer to resolving the blowback issue. Instead it made it more likely that the dispute would be litigated through the legal system, something that we wanted to avoid but apparently the builder was OK with.

Whether or not the builder decided to honor the warranty, we needed to understand the blowback problem and how it could be fixed. In the unlikely event that the builder changed course and decided to make remediation we certainly could not blindly trust them to make changes correctly.

Education was key and I was fortunate to talk to a nearby barge owner who in real life is a marine engineer who works on fuel systems for ocean going vessels.   The background was extremely beneficial. It helped to form a picture in my mind of ideally how the vent and fill pipes should be configured and to understand the consequences of the compromises.

Wanderlust’s red diesel tank vent and fill pipes.

By the end of 2015 we had been pushing the builder hard to repair Wanderlust’s fuel system issues and the many other defects on the boat that the builder had left unaddressed. At an impasse, in early 2016 we offered to ship Wanderlust back at our expense to the builder’s plant in the British Midlands for warranty work. Though we were clear that we might seek to recover the shipping expense through legal channels later, if we weren’t reimbursed before, we were certain that our proposal was the cheapest and easiest way for the builder to do the remedial works.

In response we received a letter from the builder’s lawyer: All subsequent communications were to be done through legal channels. Wanderlust’s unresolved warranty issues had morphed into a full-fledged legal dispute. With the letter from the builder’s lawyer we had no choice but to hire our own solicitor and proceed with the dispute through the UK legal system.

It took two years and £47,000 of solicitor and surveyor expenses on our side before a settlement agreement was signed in early 2018. Until the dispute was settled we could not make repairs lest the builder claimed later that he planned to fix the problems himself. For the time being we could only wait and watch as the problems continued to develop.

An alternative vent route for the white diesel tank being tested.

The vent hose was routed to through a deck hatch.

With the signing of the settlement agreement the challenge shifted to figuring out a workable plan that would reliably address Wanderlust’s fuel tank venting issues. We had talked to a number of friends, surveyors, and boatyards about solving the problem. Though everyone agreed that it would be best to install wide-bore vertically integrated vent pipes, no one was sure about the best way to accomplish it.

In the end Phillippe Gerard, the co-manager in charge of the workshop at H2O in Saint Jean de Losne, had a good suggestion: An alternative venting arrangement could be tested with a temporary set-up before building anything permanent. If the test were successful it would rule out the need to reconfigure both the fill pipe and vent pipe, a more invasive task.

As a first step it was decided that the easiest non-invasive way to install a test vent was to take advantage of the two tanks 5” wide tank inspection ports. It played off of the suspicion of mine that the inspection ports had been opened for venting in the plant the first time Wanderlust’s tanks were filled in the plant. Otherwise, how did the builder manage to get 1000 L of fuel in the tanks at the plant at a claimed 50 L/min when we could not get anything close to that amount fuel in by filling as slowly as possible?

Red diesel foam appears in the vent hose at the end of a test fill.  The amount of foam in the hose a couple of meters from the fill point makes it clear that the original narrow gauge horizontal vent next to the fill pipe must quickly fill with foam.

Adding fuel to the white diesel tank to test the new vent arrangement.

Instead of just opening the ports, which really was only practical when the tanks were completely empty, we would use the access ports as places to attach temporary vent hoses. Because the inspection ports are on the top of the tanks, they necessarily resulted in a vertically attached vent. The width of the port would also allow for a desired wide-bore vent hose. Though position on the tanks would not be ideal, a wide bore vent hose vertically connected to the tank was the best arrangement that we could easily test. It seemed to have a decent chance of working.

Thus with Wanderlust’s fuel tanks empty, H2O fitted an inspection port cover with a hose fitting to the top tank. Once connected to the tank, a wide-bore hose was run as vertically as possible to the cabin roof. With this temporary vent in place, the white tank was filled at 40 L/min, as fast as possible with the boatyard’s pump. All the time we were monitoring the translucent vent hose. Suddenly a mass of diesel foam shot up the hose reaching a height of about a meter above the top of the tank. Just as the foam appeared the pump’s automatic shut off was triggered. When the fueling stopped the diesel foam quickly subsided back into the tank. For the first time the tank was completely full and there was no blowback through the fueling port.

A similar test with the removable vent attached to the red tank inspection port was also successful.

A hole for the new white tank vent cut into the top of the tank.

From the experiments it was clear that wide bore vertically integrated vents would allow blowback-free tank fills. It also demonstrated clearly that the original narrow bore horizontally mounted vents had no chance of ever working. The volume of foam we saw coming up the hose in the more ideal vertical test vents would easily overwhelm the much smaller vents installed, even if they drained cleanly to the tank.

Now it was time to consider more permanent solutions.

The easiest and most important tank to deal with was the white tank, which gets filled more regularly. After considering the alternatives, it was decided to weld on a stainless wide bore pipe onto the top of the tank. While the hull was cut open to allow repairs from the inside of the leaking white fuel tank it was possible to cut a hole through the top of the tank and install the vent. In place the new vent pipe runs vertically 1.9 meters through the closet to the bottom of the dash. From there the vent pipe connects to a smaller translucent hose, which snakes upward to a flame arrestor mounted on the front of the wheelhouse. While there was access inside the fuel tank, the original white tank vent was blanked off, per our surveyor’s suggestion.

The pipe for the white tank vent runs up the side of the guest room closet.

And connects to a translucent hose that goes to the vent fitting on the front of the wheelhouse.

While Wanderlust was still on the hard, after the plates of steel cut from the bottom of the boat to access the inside of the fuel tank were welded back into place. Once the tank was sealed we tested the new vent arrangement by filling at 40 L/min. The permanent vent worked perfectly; there was no evidence of diesel foam rising into the translucent hose at the top of the new vent pipe.

The final solution for the red tank vent is more complicated. The red tank sits entirely under the saloon and galley. Installing a vertical vent would invade the living space and damage the woodwork. There’s some chance that a wide bore vent can be angled up from the top/side of the tank, though this will be complicated to execute. So for the time being we have an improved version of the test set-up with a high quality quick connect fitting that we can install on the top of the tank before each fill. Unlike for the white tank, we’ve kept the original vent in place, as fuel tanks need to breath under ordinary non-filling conditions. The temporary vent works well and is not particularly inconvenient. At the least it gives us more time to consider alternative permanent vent arrangements for the red diesel tank.

The detachable red tank vent hose: This hose is easily stored and vents the tank through a ceiling hatch.

A slick industrial cover seals the vent hose connector on the inspection port.

In the end we walk away from this issue confused why the builder stuck his head in the sand and refused to make the changes to make Wanderlust conform to the RCD standards. The only thing we can think is that he didn’t want to establish a precedent: If he fixed Wanderlust’s blowback issue he’d be on the hook for dealing with other boats with the same problem. Though it might not have been particularly difficult or expensive to fix Wanderlust, the costs of fixing several boats with this problem would have added up.


* At the time, we could not rule out drifting fuel level displays. Over time we established that this was not the problem.

When the builder was on board in 2016 for his legally allowed dispute inspection he had on hand a CAD drawing of Wanderlust. The drawing showed the capacity of the red tank as 1070 L rather than the 1200 L on the contract and official documents. This tank, along with the black water and freshwater tanks, were smaller than contracted. So in retrospect at the time of the first fill we pretty clearly did not have accurate information about the tank sizes. Indeed the usable fuel capacity of the red tank was closer to 800 L than 1200 L. Nevertheless, we should have been able to just squeeze in enough fuel to match the tanker delivery company’s requirements.

**In the course of the dispute we did later pay for a survey to evaluate Wanderlust’s broad RCD conformity. For this survey we naturally contracted a RCD expert and not by a member of the notified body, as later is not really an option, despite the builder’s claims. The expert’s report noted 20 places where Wanderlust did not conform to the law as laid out in the RCD standards, including the fuel system issues discussed in this post.

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