[aes256]

At the same time, I assume a standard like that only applies to people designing drainage systems for sale within the EU.

Presumably if you are a corporation looking to design and sell drainage systems, £720 to gain access to the relevant standards is a relatively small cost in the grand scheme of things.

[willyt]

Nope, these apply to the design of any building with a sink or a toilet in it. That's just the standards for the drainage pipe sizing, layout and design of pipe bedding and cover. To be fair, for a very simple building you can probably get enough information from a manufacturers website to get by, but then you don't know how much of what they are telling you is sales patter designed to make their product seem like the only solution to the problem. For example, there are more than 320 standards referenced in the domestic version of the Scottish Building Standards and while you don't need access to all of them there are plenty that are very useful to have access to.

[saraid216]

Sure, but what if you think you could come up with a way to design a system for cheap and you want to make sure your system is compliant with code?