Quote:
Originally Posted by sphelps
First off don't lower the full siphon pipe yet (primary, one with gate valve). This won't increase head pressure or flow, this is set by the gate valve and nothing else. Lowering the height will only drain more water to your sump and that's a pretty big overflow you got there. You may need to lower it if it's creating a vortex and sucking in air but I don't think that's an issue.
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Actually lowering or removing the primary drain standpipe will make life a lot easier in this configuration and it has everything to do with "head". Everybody remembers their first go at trying to adjust a herbie style overflow, even if you did shell out the bucks for a gate valve it can be a complete PITA to try and maintain with the primary standpipe that high.
However if you were to remove the primary drain standpipe and close the valve controlling that drain until the water level in the overflow stays within and inch or so of the top it so it's quiet as well it becomes much easier to do minute adjustments. The reason for this is the pressure built up in the box remains constant when it is at at given level, with a high drain pipe you get much less drain pressure and it fluctuates somewhat making it difficult to adjust. The force of the water is "static head", not to be confused the the "head pressure" we try and work out when sizing a return pump.
Some things to consider in this configuration; When the pump shuts down you will drain the entire overflow box, make sure you have room to catch the water. Also you are at a slightly increased risk of clogging the drain, make sure you open it up once in a while to flush built up gunk. You should be doing that in either configuration though.