We went through the Bahamas last year and had a great time. There are places we want to visit again and new places to see. So far our favorite stop has been the more remote island of Mayaguana.
A vented loop shouldn't add much resistance, it's pretty straight through, I think your guess of a foot of head is a good one. Putting in a vent and breaking the syphon action does eliminate the "credit" you get for the down slope of the piping past that point. So you have to count the static head up to the vent, and then not subtract the reduced height to the discharge.
Not sharpening my pencil too much, but with 2 in ID smooth bore pipe or hose, and that pump I'd expect between 1500 and 2000GPH in the system you describe. Getting a better estimate than that is probably beyond the precision of the data we have available.
FYI, To measure the flow from my bilge pump, I ran the pump until it first sucked air and turned it off. I then added a measured amount of water (12 liters) to the sump, and then ran it again until it sucked air and called that the time to discharge 12 liters.
---In amelyachtowners@..., <lokiyawl2@...> wrote :
Have a great time in the Bahamas. We have spent quite a bit of time over there on various boats over the years.
What a great resource you are. It will be intersting to compare the actual test data to the predictions. If I decide to add this pump, I think that I can get by with only 6-7' of piping which would be 2" smooth bore fiberglass piping with a length of hose to connect the pump to the piping. No elbows but some gentle bends. Can you tell me the losses to expect in a vented loop? This would also be fiberglass pipe so I can make the radius the optinum curve. I assume that some energy is returned as the fluid is falling from the vent to the discharge but have no idea of how to calculate that part. The 4 foot actual lift might be 3 1/2' but the vented loop may add another foot?
The Seland pump can be an ongoing offer and maybe if you want I will also send down the 4000 pump for you to test as well if it is of interest.
SV Sueno, Maramu #220