Furious , anybody any advice other than a stiff drink?

Thanks Dave, I said that the area was about four times (rough calc in head) and I assume that it will allow that many times the flow, but I don't know if that's how it works. If the pipes are below the water level all the time I guess that would be right but, if not, there may be some rather esoteric (to me) calculation.

 

According to Google, the circumference (bore) of a 9-inch pipe is 63.62 sq inches; The circumference of an 18-in pipe (double that of the 9-in pipe) is 254.34 sq. inches, so although double the diameter the available 'bore' is more than four times that of the 9-in pipe.

Therefore, if my thinking is straight, the two 18-inch pipes are equivalent to at least 8 of the 9-inch pipes (and in reality, it would probably be more like 10 if I could be bothered to work it out )

EDIT - must type faster!

 

Sorry fc, it's still four times

One 18" pipe is four times one 9" pipe.
Two 18" pipes are still four times two 9" pipes.

 

I'm confused.com now - so how many nine inch pipes would be the equivalent of the two eighteen inch ones then?

 

Four.

 

Of course it is! See, I can be sooooo thick at times!

 

Yes, flow and pressure are totally different things. How well the pipes work will be affected by the speed of the flow and where the pipe is in relation to the surface of the water. The pressure depends on the speed and the flow. So the amount of water passing through the pipes (flow) can vary depending on the pressure. The diameter of the pipes and the amount of solid surface between them changes the proportions.

If you want to do your head in , have a read of this:-

http://en.wikipedia.org/wiki/Bernoulli's_principle

 

I won't bother shiney - I've no chance if I can't even get the number of pipes right

 

Dave, I think we may be talking at cross purposes. Your second line of the equation says that 2 x 18" pipes equals 8 x 9" pipes. Eight being four times two.

That is what I said in my first quote but I misread fc's last question . So I answered incorrectly to that one . When I said 'four' I meant four times the number of 9" pipes. (A stupid mistake for someone, who taught maths, to make!! ) Can I report myself for stupidity?