Re: Vented tumble dryer – new vent now drying more slowly.
A possibility that the new hose has collapsed or is badly kinked. Modern vent hoses are not as robust as they used to be and do need very careful routing to prevent them from collapsing or kinking. A turn of any kind is not good news.
Easy way to test, pull the dryer out and try it without the hose fitted, or put your hand over the vent outlet outside and you should be able to feel a decent flow of warm air.
Was the outside vent new as well?
Some of these are supplied as dryer vents when in fact they are for cooker hoods as well. They often have a very fine plastic mesh covering the outlet which will very quickly get blocked if used for a dryer. In most cases this mesh can easily be removed.
Jim.