Webasto fuel pipe size

[starman]

I'm just re-installing a Webasto Thermotop which I've moved. I know it's supposed to be plumbed to the tank with Webasto's own 5mm pipe but the previous owner used conventional 3/16in soft copper instead. As a result I have a length of feed pipe from the tank in 3/16 and a similar short length from the Webasto - whose inlet pipe has also been modified (not very well) to take a 3/16 fitting. And a gap in between the two! I also have a new fuel filter to accommodate.

So the question is, do I somehow try and adapt the present 3/16 ends to take 5mm throughout or go the simple route and just use 3/16 pipe everywhere? Webasto say using their pipe is very important but the heater did work before. It certainly won't be easy to sort the Webasto end either - the flared end of the inlet pipe has been cut off and a 3/16 olive crammed onto the end of the slightly bigger pipe. (The inlet pipe is integral with the burner too so can't be replaced.)

 

[Ex Brummie]

The difference between 3/11 and 5mm is negligible. The reason 5mm is recommended is to enable the fuel pump to be able to prime itself. Trying to do this through 3/8 or 10mm will impair its operation. Use the 3/16 pipe fitted an get fittings to suit.

[starman]

21 minutes ago, Ex Brummie said:

The difference between 3/11 and 5mm is negligible. The reason 5mm is recommended is to enable the fuel pump to be able to prime itself. Trying to do this through 3/8 or 10mm will impair its operation. Use the 3/16 pipe fitted an get fittings to suit.

Yes Webasto make a big thing of their pipe being essential and it does have a very small bore size. 
The difference between 3/16 and 5mm is indeed only 0.25mm but it’s meant the installer couldn’t get a 3/16 brass olive on the inlet pipe so it’s sort of perched on the end of the pipe! Ideally I’d like to get it off and do a proper job but I’m nervous of wrecking the pipe end. 

[Onewheeler]

43 minutes ago, starman said:

Yes Webasto make a big thing of their pipe being essential and it does have a very small bore size. 
The difference between 3/16 and 5mm is indeed only 0.25mm but it’s meant the installer couldn’t get a 3/16 brass olive on the inlet pipe so it’s sort of perched on the end of the pipe! Ideally I’d like to get it off and do a proper job but I’m nervous of wrecking the pipe end. 

I very recently had to get the olive off the stub end of the pipe coming out of the Webasto to enable me to dismantle it. A bit tricky as the olive was fairly well stuck (aren't they always?) Got it off eventually with a spanner close-fitting around the pipe below the olive on the pipe end, a flat-blade screwdriver held against the end of the pipe and a molegrip pullng the two together. It really needs three hands but I did it unaided. The olive gradually moved up until I could pull it off with some gentle help from the grips.

[starman]

19 minutes ago, Onewheeler said:

I very recently had to get the olive off the stub end of the pipe coming out of the Webasto to enable me to dismantle it. A bit tricky as the olive was fairly well stuck (aren't they always?) Got it off eventually with a spanner close-fitting around the pipe below the olive on the pipe end, a flat-blade screwdriver held against the end of the pipe and a molegrip pullng the two together. It really needs three hands but I did it unaided. The olive gradually moved up until I could pull it off with some gentle help from the grips.

Neat idea, I might try something similar. 
 

[starman]

 

23 hours ago, Onewheeler said:

I very recently had to get the olive off the stub end of the pipe coming out of the Webasto to enable me to dismantle it. A bit tricky as the olive was fairly well stuck (aren't they always?) Got it off eventually with a spanner close-fitting around the pipe below the olive on the pipe end, a flat-blade screwdriver held against the end of the pipe and a molegrip pullng the two together. It really needs three hands but I did it unaided. The olive gradually moved up until I could pull it off with some gentle help from the grips.

A slightly more brutal technique in the end but it came off! Next step - decide what to put in its place ?