I am trying to extend a dishwasher drain hose using a 3/4 outlet union and jubilee clips ( that was how the man at B&Q said to do it!). But the machine hose (SMEG) seems to be a smaller diameter than the 21mm of the extension and won't accept the outlet union spigot. Is there such a thing as a outlet union reducer from 3/4"? what do I do now? Grateful for any help.