Note: Please be aware that our Pewter products are hand finished and as such can vary in appearance across their surface. Each product is unique with a mottled texture that creates an aged characteristic. This weathered or distressed look is very popular where customers are keen to avoid a shiny new appearance and require a more authentic look.We recommend all TRV's are installed on the flow rather than the return pipework of a radiator. When used in conjunction with a system automatic bypass valve this thermostatic valve can be installed on either the flow or return in any orientation. System automatic bypass valves are a specific building regulation requirement for all new installations and boiler upgrades. All bi-directional TRV's from any manufacturer require the bypass valve to function correctly and thus avoid radiator hammer.