I read you having 3 questions:

1) Each end of pipe will have an elevation you can modify so yes, it's available.

2) For instance: 1/10 = One Unit of slope for every Ten Units of travel.

The project units are used so it looks like you're in metric... In any case the slope will represent whatever the Engineer is talking in: Ask him or her!!!

3) The offset of a pipe is set in the Properties box prior to placing; once placed a slope can be added by affecting either the Start Offset or End Offset parameters. I know of no automatic way OOTB but I am not an MEP person, so someone may know of a way (or there may be a plugin)...

Sloping can be applied after laying out pipe or as you sketch pipe. If you apply it afterward all of the selected pipe Revit is recreating the pipe run but applying the slope you define. It can be complicated and finicky. Applying a uniform slope is often competitive with a desired offset elevation (invert). For example code may require a minimum of 1/4" per foot (sorry imperial units) but the resulting elevation at the accessory or equipment is undesireably "messy", like 1223.456 mm instead of just 1220 mm. In those cases it's probably better to just use a deliberate offset value. If you tag the slope of the related pipe it will likely show a slope value greater than the minimum required, but it is a minimum, so more may drain better, hopefully.

If you've not done it at all before, read through the help documentation to get acquainted with what Autodesk describes as possible.

Yes we are using Metric units.

I've spent a while reading over adding slope on the F1 help pages.

As all my pipes are already modelled i'm going to need to 'Use pipe controls to add slope to a non-sloped pipe'. It appears this section shows what I need to do.

I'm going to have to click each individual pipe and adjust one end lower than the other using the End offset values. I was hoping there may of been a way of selecting all pipes and adding a setting which drops them all from point A to point B with a slope of X.

The manual way it is. :thumbsup:

You must have missed something, select a pipe or connected pipes, click the Slope tool, adjust settings, hope the slope works for all the connected elements. Try it in some simple runs first. The more you select at once the more complicated and perhaps less likely the success.