Bottled gas lines

[Kittyhawk]

This relates to the gas installation in my motorhome.
Basically, the gas line from the bottle and regulator to the hob/oven is about 6m long. The hob/stove is at the end of the run. About halfway along the gas line there is a tee and a branch gas pipe goes to the water boiler. This pipe would be about 2.5m long. The water boiler is new and it and it's predisessor will keep flaming out 4 - 5 times after starting, and then it will settle down and function normally. We use the water boiler as an 'on demand' appliance, only firing it up when we need hot water.
The only reason for the boiler flame outs that I can think of is that the gas flow to the hob/stove is partially evacuating the boiler line and causing air locks in it. I'm out of my depth with this gas stuff and don't know if this is even feasible. Advice appreciated.

 

[ChaiLatte]

You do not say if this is a professional build nor whether both appliances were in the vehicle from new.

What gas is it? What regulator is it?

If you read the specifications of the two devices, you will find gas demand numbers. You can then look at the diameter and length of the pipe in conjunction with the gas pressure and see if it is adequate for the demand.

With (low pressure) natural gas in the UK, the rule of thumb (good for 90% of standard cases without more detailed analysis) is 22mm diameter pipe to within 1m of the boiler to ensure the allowable pressure reduction is not exceeded.

LPG will have similar detailed rules and rules of thumb that work in most cases.

Put a non-return valve as close to the boiler branch of the tee as possible. Then if your theory about the stove is justified, it will cure it.

If each appliance works OK on its own, install separate pipes and supply each one off its own regulator and bottle. Complete independence.

 

[Tris]

Sounds like bad gas pressure if both the old and new one do it. It is possible to check your system pressure with a manometer yourself. That will tell you if the regulator is providing the right pressure, and then whether you have any leaks.
Once that's checked and ok it's on to testing the flame failure device and if that passes look at the pipework for anything that may constrict the flow, including bad joints on the tee junction

I'm not a gas engineer but this is from years of caravans and motorhomes and how we'd go through it with the workshop