Thinking of fitting a kitchen sink waste? Then follow this DIY step-by-step guide

Fitting a kitchen sink waste is essential, it’s a key part of your kitchen plumbing and something you need to think about when designing a kitchen. Get it wrong and you'll have water slowly but surely creeping into your kitchen cabinets and under your kitchen floor. Any food blocked in the pipe could also potentially cause some unpleasant odours.

But it's a job that a competent DIYer can get to grips with, with the help of this guide. You’ll only need a few inexpensive tools and the essentials parts will cost very little. Here the pros offer practical advice on how to fit all parts of a kitchen waste unit to make sure your kitchen sink works as it should.

David Cruz

David has worked in the plumbing industry for over fifteen years. David has worked on countless domestic and commercial projects as a plumbing expert and gas-safe engineer. David also works closely with MyJobQuote to provide expert plumbing knowledge to homeowners, tradespeople and news outlets.

What is a kitchen sink waste?

When you finish washing up you’ve got to get rid of the waste water, but you need to make sure that your kitchen waste system is in good working order to work effectively. No-one wants a blocked sink or the stench of rotting food.

Here David Cruz, plumbing expert at MyJobQuote explains what a kitchen sink waste unit is and how it works, “A kitchen sink waste kit typically consists of a strainer, overflow and trap.” He continues, “The strainer and basket collects food debris so it doesn’t clog your drains. The overflow connects to this via a flexible pipe. This sits near the top of your sink to prevent water from flowing out over the bowl and flooding your kitchen.”

Finally, there is the P-trap Cruz adds, “Sitting underneath the strainer is the trap. This catches the debris that slipped through the strainer and prevents odours coming up from the drains.” Water sits in the bend of the trap, creating a seal to stop any smells coming back up the pipework. This is replaced with clean water every time the sink is used.

The tools you’ll need to fit a kitchen sink waste

You will only need a few tools to fit a kitchen sink waste. These include a slotted and Phillips screwdriver for the fixing screw on the overflow and the strainer. You will also need 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

How to fit a kitchen sink waste

1. Add the strainer

The first step is to add the strainer, but before you start Cruz says, “Give the sink a good clean around the waste and overflow holes.” Once done he says, “Grab the metal part of your strainer and place it in the bottom of your sink, over the drainage hole.”

The next step is to go under the sink and line up the plastic section of the strainer with the metal part. Cruz says, “Looking down into the sink, you should see a hole in the centre of your strainer. Take the fixing screw that comes with your strainer and slot it through the hole.”

To finish he adds, “Use a slotted screwdriver to tighten it. This will fix the top and bottom halves of your strainer together.”

2. Hook up the overflow

The next step is to add your overflow. Cruz says to start by placing overflow’s decorative plate over the hole in the side of the sink. “Then, take the overflow and go back underneath the sink. Line up the overflow seal with the decorative plate and tighten the fixing screws to secure it in place.”

The overflow will have flexible pipework, Cruz says, “Screw it onto the small outlet that sticks out of the side of your strainer.”

3. Assemble trap

Before you add the trap you will need to assemble the trap section. Cruz says, “This should simply screw together with plastic nut connectors. These only need to be hand-tight, so there’s no need for tools.”

4. Fit trap

Finally, Cruz says, “Connect your trap to the strainer section using the section of plastic pipe supplied in the kit.” He adds, “Your installation instructions should outline how to do this but again, there should be a plastic connector.”

To finish, “You’ll need to connect the trap to your waste pipe.” Cruz adds, “Your kit may have some plastic piping to do this with or you may need to buy this separately.”

He adds, "Either way, you’ll likely need to use a series of pipes and elbow connectors to make it fit. To cut sections of pipe down to size, you may find it easier to use a pipe cutter than a saw."

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

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.