# The Road Vehicles (Construction and Use) Regulations 1986, Paragraph 3

Extent: E+W+S

(1) Every connection for filling a fixed gas container shall be on the outside of the vehicle.
(2) There shall be fitted to every fixed gas container either—
(a) a manually operated shut-off valve and an excess flow valve, or
(b) a manually operated shut-off valve and a single check valve, or
(c) a double-check valve.
and all parts of these valves in contact with gas shall be made entirely of suitable metal except that they may contain non-metal washers and seals provided that such washers and seals are supported and constrained by metal components.
(3) In every case where a pipe is attached to a gas container for the purpose of filling the gas container there shall be fitted to the end of the pipe furthest from the gas container a check valve or a double-check valve.
(4) There shall be fitted over every gas filling point on a vehicle a cap which shall—
(a) prevent any leakage of gas from the gas filling point,
(b) be secured to the vehicle by a chain or some other suitable means,
(c) be made of suitable material, and
(d) be fastened to the gas filling point by either a screw thread or other suitable means.

---
Source: https://www.legislation.gov.uk/uksi/1986/1078/schedule/5/paragraph/3 (the official version)
Page: https://openlegislation.uk/road-vehicles-construction-and-use-regulations-1986/schedule-5/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.