The waste pipe for a washing machine or dishwasher must connect to the foul water sewer and not the rain water soakaway. The Foul water sewer can easily be identified as this is where the waste from the toilet goes. You will need to make an hole through the wall which is big enough for the waste pipe to fit through, this pipe is normally 40mm although 32mm is available.
The picture below shows a typical arrangement outside a property, you can have the waste connected to either of the two foul water drains such as the sink or the soil stack but not the rain water drain!
There are three different types of waste pipe fittings Compression waste fittings | Push fit waste pipe | Solvent weld waste pipe. The easiest way to make the hole through the wall for the pipe is with a diamond tipped core drill, these can be picked up very reasonably or even hired. Using one of these means less mess and a significant time saving compared to drilling a hole and enlarging it with a lump hammer and cold chisel.
Push fit waste
The easiest way of joining the pipe is to use push fit connectors as it is simply a case of cutting the pipe straight and removing the burrs then inserting the pipe into the fitting!
Solvent weld waste
Cut the pipe squarely and remove any rough edges or burrs with emery cloth or abrasive paper, apply a thin film of solvent cement to the pipe and push it into the fitting, this will harden almost instantly!
Compression waste pipe
Again cut the pipe squarely and remove all burrs with emery cloth or abrasive paper, disassemble the joint and place the nut and the rubber washer onto the pipe, now push the pipe as far as it will go into the fitting and tighten the nut, this will compress the washer and force it to seal against the pipe.
To cut the pipe squarely it is a good Idea to use a mitre saw, you can even get a pipe holding clamp and use a reciprocating saw to cut pipe squarely. Alternatively wrap a piece of paper around the pipe, this provides a guide to follow which will make it easy to cut squarely.
When fitting a standpipe for a washing machine the pipe must be higher than the washing machine drum to prevent syphoning.
The hole which goes through the wall should be sloping downwards towards the outside of the property, so water drains away from the appliance. If you have a grate covering a drain which leads to the foul water sewer you can merely have the waste pipe draining into that, if not you will require a strap on boss which lets you join the waste pipe to the soil stack. A hole saw will be required to cut the hole into the soil stack, it is then simply a matter of strapping the boss connector onto the soil pipe and pushing the waste pipe into the connector.