Is this a design that is acceptable?
Basically I am building a small box that will collect water pumped up by the condense drain. I will put this up in the ceiling in the furnace room just between the joists. The pump will pump the water in the box. If the 1/2" does not have a proper slope this will compensate for the lack of it; as the water level increases in the basin it will force the water to drain through the pipe.
This is intended to reduce the stress on the water pump which is currently having to push twice to push the water surplus through the existing setup. This is partially because I went all the way to main drain with a 3/8" PVC tubing and I think that is bad. When the pump stops the water trapped on the vertical segment between ceiling and joists level has nowhere to go and it drains back in the pump collector box.
That in turn makes the pump start again and the cycle repeats till sufficient amount of water is finally pushed through to stop this even when the water is coming back.
The alternative, in case I manage to give it a mild slope is to use this setup
Update:
NOt sure what is causing the water backflow that I am seeing at the bathroom end where the drain will be (for now I am using a bucket to test this)
The pump seems to have a backflow preventer as there is water in the vertical segment
Update2:
I think what is happening here is this. When the pump stops there is a hump at point ❶ in the last picture. That water will flow back and it creates negative pressure and that is causing the water movement that I am seeing in the tub despite the pump having a backflow valve
Best Answer
no you can't do that. if it connects to the sewer it needs need to either be sealed or have a trap.
Use a fatter pipe eg: (inch and a half) , support it properly and fit a proper trap on the end. the flow rate is low enough that your run can self-vent but you will need 1:100 slope
maybe find somewhere else to discharge the condensate. it's basically pure water, it doesn't need to go into the sanitary sewer.