Connecting two 90mm tank overflows into 100mm stormwater

[Bags]

I have just had a 4000g water tank delivered. The tank comes with two 90mm overflows (to match the two inlets). I was planning on connecting both overflows to a 100mm stormwater run-off pipe instead of having to run two separate 90mm stormwater pipes (about a 20 metre run). Would this size pipe be sufficient to prevent water backup in a storm?

[Buggermedumplings]

No probs, just remember that most home's stormwater discharge point is 100mm and that covers your whole house!

[davo2310]

you could cap one of them off, because they are the same height and are made for 2 for different tank positions. so they arent exactly there so both can be used