How long a horizontal run will a condensate pump support?
The &quot;lift&quot; specification of a small pump is the height to which it will raise water above itself. It is another way of specifying the pressure that the pump produces at its output port. It is not a specification of the distance over which the pump will deliver water.
As your ceiling is eight feet high and the Mars-21786 can raise water up to 16 feet, it will satisfy your needs.
You do not need to build sloping drains or use larger tubing starting from 16 feet from the pump. You can run the 3/8&quot; pvc tubing from the pump all the way to anywhere on your property where you can conveniently get rid of the water. A run of 150 feet is no problem, provided that no point in the tubing run is more than sixteen feet higher than the pump.
The effect of a long tubing run will be to slow down the rate of flow. But condensate pumps operate at a very low duty cycle, that is, the pump sits idle for minutes or even hours at a time, then runs for a minute or two to quickly empty its reservoir.
You need to be concerned more with the flow rate than with the output pressure. How much condensate does your equipment produce per hour?
I notice that the flow rate is not given for your model pump, but it certainly does not look like junk, so it will probably perform at least half as well as the more expensive Mars-21780, so 36 gph. Cut that in half for a really long drain tube, that's 18 gph.
The 21786 has a two quart reservoir. If it does what most do and starts when it's half full, it needs to pump about a quart before switching off again. At 18 gph this will take about 1 minute 12 seconds.
I suggest you do this: Run the 3/8&quot; pvc tubing from the pump to whatever drain you find convenient, switch the pump on, pour water into the reservoir until the pump starts, and observe the flow at the drain. If anything more than a tiny dribble comes out, you're good to go.