Surface Inlet Pit

[GreasyFingers]

We have just had a retaining wall constructed and needed to create a low point behind it. So we need a surface inlet pit (gully pit, sump, catch basin pit by other names) like these photos:

 

The local hardware stores and Phetchabun Thai Watsadu had not heard of them, even with the photos, and I could not find them on Lazada If anyone knows where to source one it would be appreciated. The exit drainage pipe is already in place. I know I could bodge one with concrete but would prefer the already made as it has a bigger grate than just one on the outlet pipe.

[longball53098]

The Thais use a concrete box similar to the photo but the cover is not a grate just a concrete cover with slots in it. A grate type cover would need to be made to fit. I am sure others will be along to give a more precise answer.

[Will B Good]

Does that drain into a soak away or into an onward drain of some sort?

[Encid]

27 minutes ago, longball53098 said:

The Thais use a concrete box similar to the photo but the cover is not a grate just a concrete cover with slots in it.

Pre-cast concrete pits and covers are usually available at most hardware stores.

 

 

 

 

I found these on the onestockhome.com website here.

 

 

[GreasyFingers]

6 hours ago, longball53098 said:

The Thais use a concrete box similar to the photo but the cover is not a grate just a concrete cover with slots in it. A grate type cover would need to be made to fit. I am sure others will be along to give a more precise answer.

Yes I have seen their concrete pits but that is not what I am after. I can shape a concrete collar that falls to the outlet pipe with a small floor waste grate on the top of it but would prefer the sump type. A problem with making a collar or using a pre-caste pit is that the soil is a reactive clay and there will be movement between dry and wet seasons.

 

Thanks to all the replies but it appears the plastic pit and grate is not available here.

[Encid]

22 hours ago, GreasyFingers said:

A problem with making a collar or using a pre-caste pit is that the soil is a reactive clay and there will be movement between dry and wet seasons.

You could always make a larger hole for the drainage pit and pack it with sand. That way the clay can expand and contract without affecting your pit.

 

How were you planning to drain your pit?

I am imagining a line of pits along the length of your retaining wall, all connected by 2" HDPE pipe, with the final (or lowest) pit draining into another drain or klong or something?

I say HDPE pipe because you can bury it in the reactive clay (although a sand filled trench would be better) and it won't crack or break like PVC.

 

[GreasyFingers]

1 hour ago, Encid said:

You could always make a larger hole for the drainage pit and pack it with sand. That way the clay can expand and contract without affecting your pit.

 

How were you planning to drain your pit?

I am imagining a line of pits along the length of your retaining wall, all connected by 2" HDPE pipe, with the final (or lowest) pit draining into another drain or klong or something?

I say HDPE pipe because you can bury it in the reactive clay (although a sand filled trench would be better) and it won't crack or break like PVC.

 

Only one pit with a vertical 2" pipe connecting to the stormwater pipe underneath, the area to be drained is not big, everything discharged into a catch drain. Thanks for the suggestion about the sand, I understand how it works.