A kitchen waste unit may be only a small part of your grander kitchen ideas, but it's crucial that it is installed correctly. You don’t want leaks that slowly damage your cabinets, and it will prevent food waste and debris from blocking the pipework in the future.
Plus, knowing how to install a kitchen sink waste unit yourself will save you call-out charges, and you won’t have to wait for a professional to do the job. However, there are a few simple rules and steps to follow, all of which you can find in this guide.
Jamie Heath has over 24 years of experience in the plumbing and heating sector. He has worked for both national and regional merchants. He now brings his knowledge to Build & Plumb, an online retailer supplying top-quality products for DIYers, renovators, and trade professionals alike.
What is a kitchen sink waste?
When you finish washing up, you need to dispose of wastewater, and you must ensure your kitchen waste system is in good working order to operate effectively. No one wants a blocked sink or the stench of rotting food.
Here Jamie Heath, heating and plumbing expert at Build & Plumb, explains what a kitchen sink waste unit is and how it works, “A kitchen waste refers to the fitting underneath your sink’s plughole that allows waste water to drain away, whilst catching food debris in the basket strainer to prevent blockages.” He adds, “The key components of a kitchen waste include the basket strainer, trap and overflow connection.”
Heath continues, “The trap is a curved section of pipe that sits underneath the strainer, which holds a small amount of water, creating a seal that prevents sewer gases and odours from coming up from your drains.” The final part in the kitchen waste jigsaw is the overflow. Heath says, “An overflow connection is a small hole on the rim of the kitchen sink that diverts excess water to the main drainpipe, preventing overflowing water.”
The tools you’ll need to fit a kitchen sink waste
Alongside your kitchen sink waste kit and P-trap, you will need only a few tools to install the waste. These include a slotted and Phillips screwdriver for the fixing screw on the overflow and the strainer, a microfibre cloth for cleaning (like this MR.SIGA Microfiber Cleaning Cloth from Amazon), and a pipe cutter to cut your plastic connection pipes to size.
Get the gear you'll need to help fit a new kitchen sink waste
A kitchen waste kit that includes a strainer, overflow head and flexible pipework to connect the two. Suitable for UK standard sink hole sizes from 83-90 mm
These plastic pipe cutters have a 42mm outside-diameter cutting capacity and a high-carbon steel blade, providing a smooth, strong, easy-to-use ratchet action for quick, clean cuts.
This sink trap is a multi-fit, adjustable, and telescopic P trap that meets quality and safety standards. Designed to work seamlessly with a 40mm waste pipe.
How to fit a kitchen sink waste
1. Add the strainer
The first step is to isolate the water supply and clear the area under the sink to provide space to work. Give the waste and overflow hole a good clean with a microfibre cloth. Now it's time to start adding the strainer. Heath says, “Start by taking the metal part of your strainer and placing it into the sink drain.”
He adds, “It’s important to always read the kitchen waste kit before installing it. Some kits may instruct you to apply a small amount of plumber’s putty around the strainer's flange before installation.”
Next, it's time install the strainer. Heath says, “From below slide on the rubber gasket, followed by the rubber washer and secure it from underneath with the washer and waste body, tightening the central screw to create a leak-free seal.”
Finally, he adds, “When looking into your sink, you should see a hole in the centre of the strainer. Insert the screw from the kitchen waste kit into this hole. Then use a screwdriver to tighten the screw and secure the strainer.”
2. Hook up the overflow
With the strainer in place, add the overflow. Heath runs through the process, “Go under your sink and line up the overflow pipe with the overflow flange, which is the decorative part of the fitting. Connect the overflow pipe and flange with a fixing screw to secure the connection.”
3. Assemble and fit the trap
The first step is to assemble the trap before installing it. Heath says, “Start by connecting your trap to the strainer section installed earlier. This can be done with the section of waste pipe provided in the kitchen waste kit.” You may need to cut to fit.
Next, Heath says, “Slide a slip nut and washer onto the waste pipe and connect the curved section of pipe by hand-tightening the nut.” He adds, “Align the other end of the curved pipe with the main wall pipe, ensuring a secure connection.”
4. Test unit
Verify that all connections are secure before proceeding to the next step. Heath says, “Turn your water supply back on before filling the sink and ensuring that all of the connections are secure without leaks.”
FAQs
Are kitchen sink waste units the same size?
No, as Thomas Oldham, co-founder of UK Construction Blog shares, “Kitchen waste units come in a range of sizes, and not all follow standard dimensions.” But, he adds, “Most domestic kitchen pipework has a 40mm diameter, while waste disposal units and high-end systems sometimes require 50mm.”
He adds, “A basic basket strainer should work for most sinks, but it’s always worth checking dimensions and compatibility before installation to avoid any surprises.”
Thomas Oldham has spent the past four years using his expertise of working in the engineering and construction industry for over a decade to develop the UK Construction Blog - a leading online platform dedicated to empowering individuals and businesses in the construction industry.
Does plumbing need to be certified?
No is the straightforward answer. You can tackle plumbing on a DIY basis, but it makes sense to call in a professional if you have no experience. Or, it's a complex job that is best served by a professional.
If you do the job yourself and you do it poorly or incorrectly you could be heading for a whole heap of trouble such as water leakages that cause further damage, which in the long run could cost you more than you saved on labour costs. So, if in any doubt, call in a pro.
There also the issue of home insurance as Oldham shares, “DIY installations and insurance can be a grey area. Most home insurance policies allow homeowners to carry out their own work.” But there is an if as he continues, “If poor installation leads to damage, making a claim might not be so simple.”
The insurance company may refuse to pay out on the damage if you don’t have proof that work carried out was performed by a professional plumber. Check with your home insurance provider for more clarity.
Fitting a new kitchen sink waste unit can be a simple replacement or part of a much bigger project. Check out our kitchen remodel ideas and painted kitchen ideas for some inspiration. If you’re looking to save money then our New kitchen for under 5k is a must-read.
EDITOR’S NOTE: An earlier version of this article included a quote from a purported expert whose credentials we have not been able to verify. The quote has been removed. We regret this lapse in our verification process and have updated our internal protocols to reduce the risk of recurrence.
