Seven Things To Consider When Choosing A Manhole Cover

Seven Things To Consider When Choosing A Manhole Cover

Have you ever tried to buy something over the phone, after saying “I don’t know” and listened for 10 minutes, you still didn’t get it?

This blog has broken down the process for choosing the right manhole cover. Thus, you can place the order comfortably, not trying to take notes over the phone!

Manhole Cover Keywords

Before we start, let’s go through some keywords we will use later.

What is a Manhole Cover?
The Manhole cover is a removable lid with a matching frame covering an opening hole giving access to the underground vault or pipes.

What is a Clear Opening?
A clear opening or a chamber opening refers to the hole in the ground. The size is measured from the inside of the frame when the tray is removed.

What is the Overall Size refer to?
When we talk about the overall size of the manhole cover, we mean the size of the whole manhole cover that measure from the outside of the frame.

What is Internal Tray Depth?
Internal tray depth or recess is the depth of the tray that measures from the inside of the tray. The depth is needed depending on the depth of the tile or block plus screed.

 

Choosing The Right Manhole Cover


 

1. Clear Opening

Covers are listed firstly by their clear opening size; this is because the most important part of the process is making sure the drain is both accessible and matches the existing chamber size. Having a manhole cover that fits well can ensure that the cover will perform as expected.

Find out how to measure your manhole cover.

 

2. Weight Loading

It is important to know what weight loading you require for your application to ensure a correctly specified cover is chosen.

Exceeding the maximum weight loading of the manhole cover would significantly minimise its lifetime and it could fail to lead to possible safety issues.

To find out the weight loading, you need to think about what traffic will go over your manhole cover. For example, if your manhole cover is located on a pedestrian area, domestic driveway or commercial or highway use.

 

3. Type Of Manhole Cover

Are you after a solid top cover or a recessed cover?

Solid Top Covers when fitted on the chamber opening will remain completely visible once installed.

Recessed Covers have a recessed area for infill of block paving, slabs or tiles etc. to camouflage the cover.  You should only be able to see the lifting points and the edge of the frame and tray when installed. They are commonly used in domestic parking areas, gardens and swimming pools etc.

 

4. Depth Requirement

If you decide to go for a recessed cover, then you need to find out what depth would suit your project. In other words, find out the depth of your screed, tiles or slabs you want to fill in the recessed cover.

The screed or concrete infill increases the total weight of the cover and also increase the carrying load.

 

5. Type Of Material

Each material has its own advantages and is suitable for different scenarios, either for aesthetics or type of environment. It includes galvanised steel, stainless steel, ductile and cast iron, aluminium, polypropylene etc.

Galvanised Steel vs Stainless Steel
Galvanised steel manhole cover refers to its layer of zinc coating. It acts as a protective layer to fight against rust caused by moisture and oxygen. Whereas, stainless steel manhole cover, an alloy made from a combination of iron, carbon and chromium (sometimes includes other elements) offers significant corrosion resistance.

  Galvanised Steel Stainless Steel

Corrosion resistance

Protected by zinc coating. Wear off over time. Build-in to combat rust.

Strength

Easier to manipulate while remaining decent strength. Stronger

Price

Less expensive. More expensive due to manufacturing process.

Galvanised steel manhole covers are more vulnerable to a high level of acidity and saltwater, which affect the sustainability of the manhole cover. Therefore, in places like swimming pools or anywhere with chlorinated water, near the ocean or acid rain, stainless steel is the key to avoid rust.

Aluminium
Aluminium manhole covers are very lightweight, featuring a highly aesthetic extruded construction. Despite the high quality, it is much more cost-effective than stainless steel.

Ductile and Cast Iron
Ductile iron manhole cover, an alloy made from nodule-shaped graphite. Its advantage includes brilliant ductility, therefore it won’t break when bent; slightly lower temperature limit than cast iron but still remain high strength and durability, especially high-grade ductile iron.

Cast iron manhole cover is an alloy made from mostly iron, combine with some carbon and silicone. It has high-temperature tolerance; it is strong and copes very well with intense vibrations. However, cast iron is not very ductile, which increase the risk of cracking.

Polypropylene
Completely polypropylene manhole cover features a unique slip-resistant surface with tread pattern; durable and long-lasting; lighter in comparison with ductile and cast iron.

 

6. Functionality Demand

Manhole covers for indoors or outdoors may have different requirements, such as the ability to seal and prevent odours etc.

If you have manhole covers on a lawn, they can be very unsightly. Grass Top covers are recessed covers with pre-drilled drainage holes and a double layer of factory fitted specialist membranes because grass can grow in the recessed tray while the water is gradually filtered through.

 

7. Manhole Cover Size

Many covers are standard sizes, and it is generally measured in millimetres(mm). But bespoke options are also available on required. It is a made to order service for our variety of manhole covers.