Washing machine waste going into same waste pipe as boiker2

No Need to panic, it sounds as if you have a 'condensing' boiler (pretty much all boilers are now) Part of the boilers combustion cycle is to obviously burn gas, one of the by products of the combustion is water, or, condensing water to be accurate, the boiler needs to get rid of this water, and does so usually through a very small diameter pipe (22mm plastic pipe) but even under heavy load a boiler only produces a trickle of water at best, its very similar in ways to the water that comes out of your cars exhaust pipe and for the same reasons. Adding a washing machines waste water to this, as long as the condense pipe trickles into a 40mm waste pipe is absolutely fine.