As part of my pond design for next year I'm currently looking at the returns to the pond. I plan on using an airlift from the last filtration section into a small bay/sump from which there will then be 4 gravity return pipes into the pond itself. As I'd like to return these 4 pipes each to a corner, so that they all contribute to a general circular flow, I've recognised that pipe diameter, flowrate and bends will all contribute to the tdh restriction on each pipe run and I want to avoid creating "dead" flow in one any individual pipe. I have looked at calculations for tdh and, allowing for different pipe sizes (and therefore the proportion of total flow they can take) and their length and have come up with a solution that has each pipe's tdh ending up within 50% of each other. Not bad, I thought!
However this doesn't take into account the effect of bends - the 4 runs will have either 1,2 or 3 90 degree bends. Some but not all of these can be replaced by 90 deg. curved sections or sweeps rather than bends per se, but I wanted to ask if anyone knows what sort of effects these bends would actually have on tdh?
There are some (horrificly
) complex formulae online to work them out but if someone has some simpler ideas I'd be very grateful! Is their effect minimal by comparison??Cheers, Mark