Thanks to everyone for being so helpful with my timing query.

I became ambitious and decide to try to create a program to totally automate the system which has been a real challenge!

If someone could scan my program for obvious flaws, it would be greatly appreciated.

THE PROJECT
There are two tanks callled T and Metal.T1 is for collection pre processing and Metalis for processing. We want to process for as long as possible, but need to emptyT1 when it fills.

Q1 is a pump that pumps water into the metal tank from T1.

Q2 is a pump that pumps water out of the metal tank.

I1 indicates T1 is full, which means we need to empty it into the metal tank.

I2 indicates the metal tank is full. We want it to stay full as long as possible and only empty when T1 becomes full.

I3 indicates that the metal tank is empty, which is should only be for a short period between emptying and filling it..

It takes just over 2 hours to fill or empty the metal tank.

We need to blow water through the metal tank for 10 mins every 8 hours unless it is having water being pumped out of it.

In summary, when T1 is full, the metal tank should empty itself and then fill from T1.

Thanks

Roy