The Commercial Diver Network
I noticed on the pictures a tremie concrete pour in South Africa.
Here is a tip- attach a 5 foot length of flat rubber discharge hose to the end of the tremie pipe or hose.
This will act as a check valve and keep the water out of the tremie pipe/hose and this way your concrete will not have rock or sand pockets. as long as the concrete is flowing through the hose you must keep it in the concrete pour, never let it free fall through water as the portland cement will wash out of the concrete and all you have is sand and gravel.
when the concrete pour is done the hose will close and keep water out of the tremie pipe/hose.
Use heavy duty rubber flat discharge hose for the check valve.
Flat rubber discharge hose can be used as a check valve for other requirements.