How to build a cutoff drain sump pump pit?

[kn_ll]

I am planning to install approx 35 meters of aggie pipe drain with a sump pump pit for lowering the water table. The pit needs to be 1500mm deep. For the pit I am looking at installing Everhard 600 x 600 x 600d pit with three Everhard 600 x 600 x 300d riser stacked on top making the total depth 1500mm. It is unlikely that any vehicles would run over this pit. Are there any issues with the narrower pit and is there other pits in the market that does a similar job? Further what size sump pump would be required? Note no direct rain water would be collected except what is absorbed from the surface into the ground. The ground is medium dense clayey sand, so the vertical surface collection area into the scoria would be 35m long by 1 m deep one side only, the other side of the trench would be lined with polythene.

[kn_ll]

Thanks @EricL 

Everhard's comment "can't predict what will happen or how the pit will behave when it is buried that deep" is noted, However I am still planning to install the 450 series pit as the pit would not be installed at a location where there would be vehicular traffic.  Only the occasional foot traffic.  As for pit width, there is the https://www.bunnings.com.au/karcher-sp7-inox-dirty-water-submersible-pump_p0134552 with an internal float.  Do you have any issues with this type of float?

[MitchellMc]

That Karcher looks like it would be more suited to the job @kn_ll. However, these submersible pumps are designed to move a body of water; they're not designed to be permanently installed in a pit and pump water from it in rain events. That would be a sump pump similar to the Ozito 500W Vortex Submersible Sump Pump. Although they appear to be very similar in nature, typically, a submersible pump is used when no damage can occur if it stops functioning, like draining a pool. Whereas a sump pump is designed to a higher standard and is something you really need to rely on as if it fails an area can be flooded.

Mitchell

[kn_ll]

Thanks @MitchellMc 

I am still planning this project and I have further queries:
 Please confirm I have specified  the correct parts and advise if any part missing? In particular is the check valve a special order.  Are all fittings require a socket.  

For the pit riser can I drill 32mm holes in the wall anywhere?  In particular how far from the top?

[EricL]

Hello @kn_ll 

In order to avoid a bottle neck in the check valve, I suggest reducing the entire run to 25mm. This will make it easier to join the parts together and you won't have to special order a 32mm check valve.

Here is the proposed parts list:

• Holman 25mm x 1" Press PVC Faucet Socket
   
• Holman 25mm x 3m Class 12 PVC Pressure Pipes
   
• Holman 25mm In-Line Check Valve
   
• Holman 25mm x 1" Press PVC BSP Male Thread Adaptor
   
• Holman 25mm Press PVC Barrel Union
   
• Holman 25mm 90° White PVC Elbow

If you have any other questions we can help with, please let us know.

Eric

[kn_ll]

Thanks @EricL 

I would like to stay with 32mm as it less strain on the pump motor therefore increasing it life.  Do Bunnings have a 32mm check valve?

[EricL]

Hi @kn_ll 

I'll have to double check if the check valve comes in 32mm. However, as another option you could use a 40mm check valve and use reducers at the ends so that they fit 32mm pipes. As soon as I have more information, I'll let you know.

Thanks for your patience.

Eric

[EricL]

Hello @kn_ll 

I've just been in contact with our provider and they have informed me that they don't have a 32mm PVC In-Line Spring Check Valve. There is the 25mm and then the 40mm. I'm going to stay with my original recommendation of using a 40mm check valve instead of a 25mm so that you don't get a bottle neck in the flow of water.

If you need further assistance, please let us know.

Eric