Just thought I would share this for anyone else doing a sump for the first time...
Our sump is powered by Eheim 1262s, they should be putting out something like 600-700 gallons an hour depending on head loss to various things.
This is running through 12/16mm (essentially 5/8") Eheim tubing to an Eheim spray bar (pricey but nice). This winds up being pretty high pressure given the three section spray bar so I bought some extra sections intending to go to four sections.
Our basic set-up is a herbie set-up and the straight siphon had always handled all/virtually all the flow from the Eheim. After putting in the extra section I got up the next morning and was surprised that the durso/emergency drain was taking in a lot of water.
I concluded that putting in the extra spray bar setion reduced the head pressure on the Eheim pump by quite a bit and jumped up the gallons per hour over the capacity of the siphon, which I opened from perhaps 3/4 open (using a gate valve) to full open.
So I removed the extra section but the durso was still takinga lot of water. I figured something I had done had still increased overall flow as I didn't see anythign else had changed.
The durso was somewhat noisy so this was not satisfying so I decided I would t-off the return line back into the sump to reduce flow and get things back to how I like them.
So today my t-stuff shows up and I am starting to plan how to do this when I notice something funny. The wet-dry media boxes have emergency holes in their sides to let water out and in teh hole nearest the siphon return line water is just pouring out.
Why is it doing that?
So I open up the media box (something I haven't done since getting things set-up really 5+ weeks ago) and I discover...
The section of Poret foam directly under the siphone return is simply full of mud and slime that has been sucked in and that it sits high enough that it is actually interfering with flow! so the water coming out the side of hte media box can't flow down the wet-dry and that is really what caused the flow rate change in the first place - NOT the extra spray bar section. The spray bar was just a coincidence.
So I cut out the offending section of foam to give a large open area for water to enter and magically it is back to exactly where it was before this adventure started.
My mistake was ignoring the little signs that my hypothesis - i.e. spray bar reduced head pressure leadign to more flow - was incorrect.
