It rained last night. Not a lot, but sufficient to test the guttering (sigh of satisfaction at a job well done). The gutters are working fine. Now I just need to connect the downpipes, but this needs to wait until the rainwater barrels are in place. I struggled to find any suitable connectors locally to join the rainwater barrels together; the common-or-garden 20mm diameter connectors won’t do the job because the entire contents of an 80mm diameter downpipe are entering the barrel. Elementary school mathematics reveals a problem (if a bath is filled by two taps at a rate of ten litres per minute, and drains away down the plug-hole at a rate of five litres per minute, how long will it take two men to find the missing plug?)
In other words, if the 80mm diameter pipe is carrying a full capacity of water, it stands to reason that a total diameter of 80mm is required to exit the barrel to prevent it overflowing. So the plan is to have a 40mm diameter pipe joining the barrels, and a 40mm pipe as an overflow. I was able to find some 40mm diameter tank connectors online (again from the UK), and as I already have some lengths of 40mm pipe, I can follow the golden rule described underneath the logo at the top of this page.