We've always had a low level waste with a tall standpipe. In this house the waste pipe comes out from (goes in to!) the boxed in soilpipe 25ins from the floor. This barely gives a fall from the sink waste, but I'm concerned about adding in a standpipe for a washing machine. There is room for a simple U or S trap, but that's all. Is this sufficient or will we have problems with water slopping out of the top when the washing machine pumps? Would making up a deep U be OK or will there then be too much standing water?