Having wanted to do this for years but been put off by the difficulty of installing the older, barrel-shaped tanks in a restricted space where we'd have had to dig too deep, too close for comfort to this old house's non-existent foundations, I jumped at the chance to buy one of the new shallow tanks this spring.

Of course, the weather made it impossible to finish digging out the pit for most of the first few weeks after the tank arrived but I'm now almost there - just a bit of squaring off and levelling out to do, if the baked-hard clay permits.

Next issue: how to get it in there from the fortunately unrenovated front room where it's presently sitting. Easy to walk it out the back French doors, although it's a fairly close fit. More problematic, though, is constructing an adequate bridge along the length of the existing drainage pipes (which we had to uncover so as not to damage them) so as to carry the tank down that and drop it into the adjacent pit. It's a very tight fit to get this tank into the only space available and the only safe place to foot the bridge is on the remaining few paving slabs at the edges of the excavation. Using scaffold poles to stiffen the very long planks won't work: they'd just break the slabs once serious weight (several strong men + tank) was put on the bridge. 

What I really need is to pick the brains of my pet mechanical engineer - but he seems to have disappeared off the face of the earth, yet again! Do we have any friendly engineers around locally whose brains I might tap more easily?