This is a bit of a specialised subject of mine
, as I spent about 5 years surveying sewers ,pumping stations
et al .
Firstly , the waste water should really be put down a Foul System , not a Storm System.
Herein lies the problem of recognising FS and SS AND the Combined System.
As a general rule of thumb , any property built post 1976 should have a seperate sewer system, as will the mains sewer system .The easiest and quickest way to spot a seperate system is to find a property close to where you are working and see how many inspection covers are visible. you will find that the new SS has
2 Inspection chambers , normally running parralel to each other , about 1-3 ft apart . This is indicative of a Seperate System.
As already mentioned on other replies , you then need to locate the FS within the SS - easily done by the Kitchen sink - THESE ALWAYS RUN INTO FS !!
On older properties pre 1974, the sewers are generally connected to a Combined System ,which will only have
1 inspection chamber, whereby both the rainwater downpipes and the FS pipes ( kitchen , toilets etc ) run through a single pipe . At these type of properties and the main Road sewer, you should be ok to throw your waste down any drain you see fit , wether that be on the property itself or in the main road!.
A word of caution guys is for your customers who are slightly more 'rural'. You will still encounter customers whose Foul Waste goes into a septic tank . under no circumstances empty your waste anywhere near their property as any change in the PH of the tank or the addition of detergents , acid/alkalines etc will kill the septic tank . if you are found to have killed a tank and it has to be cleaned and restarted , you could be hit with a bill in the region of £1000 !!! you are far better to take your waste with you and dispose of it in a village/town drain , plus you will impress your customers with your new knowledge of their sewage systems!!;D car washes and/or fuel stations always have what is known as interceptor tanks on site , which prevent fuel and large amounts of detergents from entering the Storm System , hence they do not have any unsuitable waste entering the sewage systems.
Finally , do not always take on face value anything that a water company tells you about disposal of your water , as 95% don't know half of what I have told you above - I had to deal with these people for 5 years! . The only way to get real accurate advice about this would to either contact a specific sewage management department at the water company or a consulting engineer who surveys sewage systems.
Hope this essay helps you all to stay fine free...