Gravity back boiler with pumped circuit

[Kitten Sniffer]

Yup. I ,mean pipe bender, not like bender. Auto corrupt is a beach on my device. Oh, have i tried to work the system using fittings rather than hiring a pipe bender, BUT... The primary circuit will have a really short run and to accommodate the required rise and fall i will need some bespoke bends (including the vent/fill tee from the flow). So, hire the kit and have as few shallow bends as necessary with no steep direction changes or obstructive fittings. Personally, not such a fan of street elbows, swept or otherwise. As they require a fitting immediately afterwards. 

[MtB]

Back in the day when I used to actually install gravity systems, I used to be able to buy 28mm swept bends with a radius of about 4".  Possibly better than a pulled bend as no slight reduction in cross-sectional area that a pulled bend gives. And definitely no rippling!