first of all use CW glands. Then use an IP washer between the gland and the box. When tightening the gland on a CW, you dont leave as much of the armour out of the sheath as you do on a normal BW gland. Make sure the olive is on the right way round, or it wont tighten up properly. Also make sure the sheath of the cable, before the point where the armour is stripped, is inside the compression part of the CW gland (the rubber bit). Make sure you tighten the compression part of the gland, but dont overtighten, as the seal will fail!
When istalling the box, ensure the rubber seal on its lid sits prperly on the box, and ensure all screws are tightened equally. Most IP67 boxes have caps that sit over the screws that you use to secure the box onto the wall, but i dont trust them, we used to use industrial sealant to cover the screw so no water could enter the box. another method is to drill small drainage holes at the bottom of the box, provided there is no way water could enter from the bottom.
However in my experience (installing water features) the only way to truly give a maintenance free waterproof connection is some sort of resin joint!
PS, some rubber seals can be tightened and still seep water. You can put vaseline on the seals and it works wonders! we used to use it on the seals in pumps and valves.
John
