A productive day!

1. Tank interconnecting pipe fitted: check.
   
2. Overflow outlets fitted and sealed: check.
   
3. Water level gauge fitted and calibrated: check.
   
4. Custom gutter cleaning tool designed and fabricated: check.
   
5. Gutters cleaned, probably for the first time in a decade: check.
   
6. First flush diverters emptied ready for the next rains to rinse out the dirty gutters: check.
   
7. Beer bottles emptied: check and check.
   

That's everything I'm willing to do myself. From here on I'm paying somebody else to finish the job. We've got overflow pipes to run underground to the street, a pump to install and internal plumbing to be done.

Well actually there's one more thing for me to do, which is to bury the connecting pipe that runs between the tanks. That can wait until after somebody has installed a t-piece in the middle of it for the pump to draw from.

Instead of a rubber... thing... to seal the overflow outlet I bought two 90-degree flanged fittings and just screwed them onto the outside of the tank with silicon to seal them. They point downwards and the insect barriers just pop onto the end of them. More pipe can be attached later to take any overflow safely away.