A 'standard' BSS surveyor cannot (by law) do a gas check/ gas work on a liveaboard - he must be 'gas-safe' registered, unless a bubble tester is fitted.
It is detailed in the BSS documents :
Carrying out 'work on the gas system of boats used primarily for residential or domestic purposes fall within scope of a piece of UK legislation known as the Gas Safety [Installation and Use] Regulations (GSIUR).
As such, the law demands that anyone contracted to 'work' on the LPG system of a boat in scope must be (LPG boats-competent) Gas Safe registered.
As the definition of 'work' covers the removal and replacement of a screw nipple on a gas test point, the scope of the GSIUR includes carrying out BSS LPG tightness test.
Therefore, on a boat in scope of GSIUR, examiners who are not Gas Safe registered can only complete check 7.12.2 (confirming gas tightness) by either:
undertaking a gas tightness test using a bubble leak detector where fitted and correctly located; or,
observing the tightness test conducted by a (LPG boats-competent) Gas Safe registered installer.
Where a BSS Examiner who is also Gas Safe registered is undertaking a BSS Examination of a boat in scope of GSIUR such as if it is a boat used mainly for domestic/residential purposes, the Examiner could potentially identify safety-related LPG issues beyond the extent of the BSS Requirements. In doing so, they may feel duty-bound under their Gas Safe registration to report and discuss the additional issues.
If in discussions additional works are agreed as necessary and the Gas Safe registered Examiner is chosen to carry out works to remedy the safety-related LPG issues, this must be undertaken by way of a contract that is entirely separate to the contract for the BSS examination.
Does a bubble leak detector do away with the need for a Gas Safe registered engineer testing the gas system on residential boats?
Yes, because any BSS Examiner can check for leaks using a fully functioning and appropriately located bubble tester.
It is the case however that there is no BSS requirement for a bubble leak detector and so fitting one is matter of boat owner choice.
Note that all other types of gas work, such as adding or replacing an appliance, needs to be conducted by a Gas Safe registered engineer with the LPG boat competence listed on his/her identity card.