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Buying a Replacement Manhole Cover: A Detailed Guide

buying a replacement manhole cover a detailed guide blog post header image

Buying a Replacement Manhole Cover: A Detailed Guide

Replacing a manhole cover might look like an easy job – after all, if you can lift the old one up, putting a new one down isn’t going to seem like much of a challenge.

The trouble is, it’s rarely (if ever) that simple when it comes to manhole covers. In fact, we get more calls about manhole covers than virtually any other underground drainage pipes we stock.

With this in mind, we’ve put together a detailed guide – walking you the things to consider and steps involved with replacing one, how to choose from the manhole covers on the market, and a few additional underground drainage parts it’ll be helpful to become familiar with.

Key Takeaways:

  • Manhole covers are measured by their “clear opening size” rather than the overall frame. So bear this in mind when looking for a replacement.
  • You should replace both the frame and the cover when replacing a manhole cover.
  • Pick the correct load rating for the replacement cover.

Manhole cover jargon

It’s useful to know a bit of manhole jargon and names for different parts of the system. Although ‘manhole cover’ is the name we’re all familiar with, it’s probably more accurate to call these products ‘drain covers‘ or ‘inspection chamber covers‘ – since it’s an inspection chamber they’re sitting on top of.

Generally, you’ll buy a cover with the corresponding frame that it sits in. This is an important point and something that often causes people problems when they replace a cover.

You will hear the term ‘Clear Opening’ when looking into manhole covers, this refers to the size of the opening in the frame underneath the cover and is more important than the size of the cover that sits on the top. You will need to ensure that you have this measurement when sourcing a new cover as this should be the same size or bigger than the inspection chamber below to ensure easy access to the chamber should this be required. The image below should help you to have a full understanding of what this term refers to.

diagram showing where to measure manhole

Why can’t you just swap manhole covers?

Unless your manhole has been very recently installed, there’s a good chance that you won’t be able to find a cover that fits perfectly in the frame you’ve already got.


Well, it’s really because frames and covers are designed to fit together perfectly. Even if you do find a cover that seems to fit, there’s the very real possibility it won’t have the same overall strength when it’s paired with a frame it’s not made to sit in.

In some cases, frames and covers that aren’t designed to work together have led to serious accidents.

In short – this is a job that needs to be done properly – as much as you might not want to, your installation is probably going to have to involve replacing the frame and the cover.

What are recessed covers?

Today, virtually all manhole covers are designed so they fit flush with the surrounding surface. This is obviously an important health and safety consideration anywhere – but especially in pedestrian areas, driveways, car parks, or areas that see any foot or motorised traffic.

The thing is, even if they sit flush, black grates and manhole covers aren’t exactly works of art – so if you’ve got an inspection chamber that’s under the block paving of a driveway or somewhere else with a decorative surface, you’re going to need a recessed cover that will allow you to effectively hide the cover.

photograpgh of recessed manhole cover in a patio

How does a recessed manhole cover work?

A recessed cover usually has at least a couple of inches of recess, dropping the actual cover beneath the height of the surrounding frame and allowing you to block pave the cover.

You’ll still be able to access the lifting key points so you can use tools to access the opening underneath – so they’re not completely camouflaged – but they’re often considered more attractive than manhole covers that sit on the surface.

You can fill the recess with a finish that will suit the texture and colour of the surrounding area – blocks, slabs, tarmac, or any driveway finish will usually work perfectly.

What kind of manhole do you need?

If you take a look at our range of covers and inspection chambers, you’ll see there are lots of different sizes and figures to consider which we will explore below.

The first thing to think about is the size you need.

Measuring a manhole

Materials, designs, and styles vary from manufacturer to manufacturer – but the one thing that never changes is the way their products are measured.

The measurement you need is the distance between the walls of the frame with the cover removed – the clear opening. This measurement will be the diameter for round chambers – or centre-to-centre on square shapes. Double-check this on the system you’re replacing then note the measurement down – you’ll be looking for this on the products you’re replacing them with.

Load capacity

Next up is the ‘load capacity’ – essentially how much weight the product can safely support.

Now, different covers have different load capacities for different applications and services. This is essential information to consider if you’re keen to avoid any people, cars, or lorries falling into your drainage or services access system. If there will be heavy traffic passing over the cover, you’ll need a heavy duty manhole cover.

The different maximum weight classes are:

A class (A15 – 1.5 tonne loading)

Suitable for light use – such as paths, patios, and garden. Most recessed designs are A15 class. Usually made of plastic or steel.

B class (B125 12.5 tonne loading)

Designed for light pedestrian traffic and house driveways. Usually galvanised steel, ductile iron, or plastic composite.

C class (C250 25 tonne load)

Made for light traffic areas with slow-moving cars and vans. Again, usually galvanised steel, ductile iron, or plastic composite.

D class (D400 40 tonne loading)

Intended for main road use and public car parks.

E class (E600 60 tonne loading)

Suitable for very heavy duty areas like loading bays, warehouses, and industrial parks.

F class (F900 90 tonne loading)

Made for the heaviest applications – including docks and runways.

If you’re not sure which load capacity is going to be right for your application, feel free to give us a call – we’re always happy to help you decide which product is right for you.

Do you need plastic, iron, or galvanised steel manhole covers?

Today, a polypropylene plastic manhole is generally every bit as strong and durable as an iron one – so material choice doesn’t matter as much as it used to. Galvanised sheet steel covers tend to be a little lighter and easier to install than some other materials – so these tend to be popular products.

Generally, composite covers are the most cost-effective – with our range starting at just over £30 ex VAT. Ductile iron is a touch more – starting around £52 ex VAT – and, as you and imagine, the price moves up along with the maximum weight the product will hold.

If you’re working with the correct load capacity, the material you choose can really comes down to what will look the best for your application.

Should you choose a square, triangular, or round manhole cover?

Again, much like the material you choose, the shape of manhole you choose is also likely to be driven by what will look best – although there are a couple of factors to think about beyond aesthetics.

Round manhole covers cannot fall in on themselves – and the properties of the circular shape make them the most resistant to any earth compression around them.

Some drain covers that rectangular or square shapes are actually split in two – forming two triangles. This shape is often used on roads as it is less likely to rock backwards and forwards, limiting wear and preventing damage to vehicles from slightly raised edges.

double triangular covers and frames are often used on roads and motorways

Need to talk to the EasyMerchant team?

We get dozens of manhole questions every month – so if you need any more information about anything you’ve read here, just get in touch with our friendly customer service team on 01371 850 120 option 1 and we will endeavour to assist you.

Whether it’s further details about installation, how to measure your current fittings width, the tools needed, our range of accessories – or anything else, we’re on hand to quickly fill you in on everything you need to know!

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10 thoughts on “Buying a Replacement Manhole Cover: A Detailed Guide

  1. avatar of mike bridges
    Mike Bridges says:

    I need to buy some 470mm plastic drain risers from you so can you tell me if this is internal measurement or external
    I also need round covers to fit which don’t need to take heavy loads, can you advise what covers I need

  2. avatar of alistair brunning
    Alistair Brunning says:

    I’d like a recommendation for a contractor / company I could get in touch with to arrange for an assessment drain cover replacement, please. The damaged cover is in the centre of a pavement next to a small road, so the load capacity would need to be B Class B class (B125 12.5 tonne loading).
    Thank-you very much

  3. avatar of sanjiv roy
    Sanjiv Roy says:

    Hello, I find this article is very helpful. As companies like Crescent Foundry manufacture different types of manhole covers of different sizes and widths it is not easy to swap an old manhole cover with a new one. You need to keep various things in mind while choosing.

  4. avatar of colin palmer
    Colin Palmer says:

    I have a round manhole cover that screws on. It is only a couple of months old. I wish to replace the cover with a square one with resin over the top. Can this be done if the original is fixed by srews/bolts?

  5. avatar of amy
    Amy says:

    Hi, we want to install a patio in our garden, however we have a manhole there. We want to use a recessed manhole cover but our internal dimensions are 480mm x 620mm. Could we use a standard 450 x 600 cover? Or can you recommend one that will fit please?

    Thank you!

  6. avatar of tony marcangelo
    Tony Marcangelo says:

    Based in EN7 5HB Cuffley Herts the corner of my existing cast iron cover has cracked the covers external measurements are 81 cm long 51 cm wide although from reading your articles it looks like i would need to replace the frame and cover. Do you know of a reliable contractor in my area that could quote for replacement – my neighbour is in a similar situation so there may be two jobs on offer

    • avatar of lainey wykes
      Lainey Wykes says:

      Hi Tony,
      Unfortunately we are unable to direct you to contractors and we do not stock any manhole covers in the size that you are looking for. If you are able to give us the brand, load rating required and the size of the clear opening we can speak to our suppliers and try to source one for you.

  7. avatar of rodney bowman
    rodney bowman says:

    i have been looking for a vintage cast iorn inspection cover 19.25 x 25 inches found one ebay payed for it only to find collection only managed to get credit back ebay seem to have loads diffrent sizes all free to collect i would have agreed to pay postage

  8. avatar of howrah ferrous limited
    Howrah Ferrous Limited says:

    There is something that should be considered when selecting the manhole covers to use the manhole cover effectively & It’s really important to choose the right manhole covers on the market. Thanks for the important tips it’s really considerable to our industries.

  9. avatar of malcolm
    Malcolm says:

    Ive got a 20″ x 25″ (approx) imperial sized cast iron flysh mounted ma hole cover and frame. Can i get a replacement one but that is recessed to allow it to be fitted into a patio?
    Or do i have to make a 600 x 450mm metric one fit?

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