How to raise storm water pit or grate 15mm?

[PatDIY_Dad]

We've got 2 of these Ever hard storm water pits with plastic grates ( but I am going to soon change to aluminum steel ones)

these grates are under our alfresco pergola which we are going to get tiled in a couple of months 

The tiler told me the pit has to be 15mm higher so it sits flush against the tiles

The floor at the moment is all concrete 

The grates are removable but the pits a solid and won't move

Does anyone have any ideas on how to raise it up a bit ?

Photos below with the black and yellow spaces equal 15mm so has to go flush with that 

 

 

[JacobZ]

Hi @PatDIY_Dad,

Thank you for your question about raising a stormwater pit to accommodate tiles on your alfresco patio area.

The only way I can see that you can raise the grate level is to remove the existing pit and bring the base up by 15mm before reinstalling.

Is there any movement at all with the pit? Or is it solidly cemented into place? 

If you can lever it out with a chisel or flat-head screwdriver, that would be brilliant, but if you can't, you may need to cut the pit out with an angle grinder with a cut-off wheel and replace it with a new Everhard EasyDRAIN Polymer Grate And Floway Pit. If you need to use an angle grinder, please remember to wear gloves, a mask and eye protection.

Once you've gotten the pit out, you may need to add a small extension to the stormwater pipe for it to reach the outlet of the pit. If you could provide the dimensions of the pipe, I would be happy to recommend something suitable.

To raise the pit, the Installation Instructions recommend bedding sand such as this Easy Mix 20kg Paver Bedding and Screeding Sand. Make sure that the bedding sand is compacted well to avoid any movement in the pit. 

You will also need to seal the bottom edge of the pit to the concrete with a bead of sealant such as this Sikaflex 11FC Plus. You might like to check out How To Silicone a Gap for an example of this process.

As you would be raising the pit out of the ground, creating a trip hazard, it might be worth getting yourself prepared for the job, but waiting until closer to the time the tiles are installed.

Let me know what you think.

Jacob