I had a quick look at the manual on their site and it looks like the pump has female threads into which you insert the elbows which reduce to 1" hose. These will be 1" or 3/4" female bsp. You can get standard brass fittings which will take you to 15 mm if thats the pipe size you are using . If you want to use 1/2" hosepipe with jubilee clips then you will be able to warm up the hosepipe and slide it over a bit of 15mm copper fitted into the brass reducer. The fitting will be either 1" male bsp to 15mm compression or 3/4" male bsp to 15mm compn. Looks like you will need two of them. I suggest you take the pump to a local plumbers merchant in the morning and also take the pipe coming from your hf5 and they should be able to sort you out. Tell them spongebob sent you and they'll look after you.