I am about to install a Salamander ESP100CPV shower pump. The easiest
place for me to put it is in the airing cupboard above the Hot Water
Cylinder. The intructions indicate that I can do this as long as I fit
an anti-gravity loop at least 250mm in depth.

OK, all well and good but at the risk of sounding foolish, is this
something I can buy ready made or do I need to construct one ? If the
latter, what is the best way of doing this in 22mm copper, I don't have
a pipe bender. I guess what I'm really asking is will there be any
problem if I form one out of short straight pieces of pipe with 2x
90degree elbows ?

Thanks.