Raising older larger style manholes

[shabbaranks]

Hi guys,
As Ive more time on my hands with all this lockdown stuff Im tidying up the garden. Ive got a couple of large older manholes which ideally I'd like to raise but I cant find any risers big enough??

The manholes are 600mm (rectangle) and I need to check the round one but does anyone know where/how I can do this? Ive read some people just cover them but I don't think thats a good idea???
Thanks as always

 

[CBW]

Good morning,

As far as I know, the rectangular ones are brick, so would just need building up to suit, the circular one might just be a riser required.

 

[shabbaranks]

Thanks Chris Im no builder so my brickwork might need some practice will have a go and see what happens. Im guessing there are no issues with doing this as this drain is for soil waste (the round is rain etc) not sure what the technical terms for these are

 

[CBW]

Correct soil waste, although a lot refer to it as foul waste. The other is classed as rain or surface. The manhole cover needs to be mortared in as well.

 

[shabbaranks]

Ive just lifted the cover and your right its seems relatively easy to add some blocks to raise it and then replace with one of the newer\lighter covers. This might sound like a stupid question but what sort of blocks would you use to raise the manhole cover? Ive got some spare driveway blocks but Im assuming they wont be correct?

Thanks

 

[CBW]

I’ve never done one, but I wouldn’t have thought blocks wouldn’t be ok. I’d be going for engineering bricks such as https://www.wickes.co.uk/Class-B-Red-Engineering-Brick-65mm/p/174990. Maybe @HERTS P&D or @Hugh Jaleak could confirm?

I’ve tagged these fine chaps in, because they’ll have done this sort of work.

 

[Hugh Jaleak]

Round chamber, 450mm risers are required to raise height to suit, but you'll need to see what the existing manufacturer is, and get same to suit, not all are interchangeable.

The others, depends on construction of chamber under the cover, engineering bricks would be required for a manhole. They may also be shared drains, in which case are the Water Company's asset, and you would be wise to gain written permission before making any alteration to these.

Edit, should add for the OP, the shape of the cover is totally irrelevant to what the drain is carrying. Some heavy duty covers can sometimes be marked with FW or SW to indicate Surface/Storm Water or Foul Water, and there was a school of thought some years ago that the triangular covers should be position to point in direction of flow, but that never seemed to become a rule of thumb.

Best cover by a long shot is a round one, gives more room to access the chamber below and the added advantage you cant drop the bl00dy thing down the hole.