## Flow rate of water dropping out of a pipe

 Are the pipes filled with water? If the water merely drips from the end,

Your point about a local hump in the pipe trapping an air bubble is a good one, however.

 Quote by anorlunda Are the pipes filled with water? If the water merely drips from the end, it suggests that much of the pipe volume is actually filled with air. If so, then changing pipe diameter will have little effect. If the slope of the pipes is not uniform, it is also possible to trap an air pocket in a high spot of the pipe. that will reduce the effective diameter.
After 30m the water flows out of the pipe quite fast, considering that the fall is only 1-2%. But the diameter of the pipe used by the outflowing water is only about 30%. So yes, you are right that a lot of the pipe is filled with air and that's the frustrating part.

My original question had a lot to do with why the pipe is delivering so little water. It's possible that there is an air pocket, but it's also possible that there are roots in the pipe. I do clean the pipe every year and in doing so I remove a small amount of silt and fine roots from the pipe, but this only increases the flow marginally.

The conclusion so far is that there is no sense in dividing the pipe into 2, which would facilitate better cleaning and inspection, because that would not increase the flow of the 2 halves. Why not, is not clear to me, but I accept the advice on this point.

Perhaps you could explain, if the head of water is caused by the dimensions of the pipe, why can't I remove the head by reducing the dimensions? I can see that the diameter of the pipe is a restriction to the flow, but I don't see why the length of the pipe is not relevant. I can't imagine the water not flowing through the pipe if it were only 30cm long instead of 30m, because the friction loss would be so much smaller.

If I had an open pit 30m long with a 10cm inlet and outlet, are we saying that the outlet would not allow any more water to pass than it does now?
 My advice is to cross a local farmer's palm with silver. Since you live in an area of good surface and groundwater many farmers will have a land drainage plough such as this. You could get a new P2 pipe in plastic installed easily and cheaply this way, but go for at least 6 inches. A 30 mete run is almost nothing, This pipe comes on 100m+ rolls. Much smaller machines are also in use but you get the idea from here. http://www.mastenbroek.com/land%20Dr...ricultural.htm