Recession times = luxury industries suffer. While Australia is no longer in a recession, things can be slow as consumers spend less on luxury and also become more price sensitive for essential items. This advice applies to all trades businesses but we've used plumbing as a specific example.
Change the focus of your plumbing work - Luckily, plumbing is a good combination of essential services and luxury items (like installing a new bathroom or spa bath). Be prepared to pick up the less lucrative jobs like fixing pipes or leaks will ensure that your business maintains it's cash flow. In good times plumbers can pick and choose the jobs they want, but this is often not possible in a recession. This is often true for many trades businesses - not just plumbers.
Competition - when demand lowers so do prices, so make sure that you're doing your research on your plumbing competitors pricing more regularly than you would in stable times. It's not necessary to drop your prices drastically, but your plumbing rates must remain competitive.
Marketing - in a recession plumbers must still market and let your prospective customers know your business is ready to do work for them. However, you might want to change the focus of your marketing away from luxury items like new bathrooms or kitchens. Mention repair services either specifically or generally, but still include the luxury items. Change your Service Central profile to include all the items in your category and keep an eye on the Open Jobs Board for odd jobs you may want, or speak to your account manager about extending your profile (there are both high and low cost options here).
Focus on the locals - if you've got extra time, put that time into creating relationships with local businesses. Introduce yourself and your services to local restaurants, real estate agencies, hair salons etc. Join a small business club and network, or spend more time on the internet looking at forums and social media.
Cut costs - obviously your plumbing business is always focused on keeping costs low and profits high. Look around for alternate suppliers, negotiate discounts etc. This legwork will stand you in good stead when the recession retreats.