Length of bildge pump run
- Thread starter sailnewbie
- Start date
yup. The big pump is now the emergency pump (albeit a small one,) and the little one takes care of nuisance water.JGW: I think a lot of guys confuse a bilge pump with an emergency de-watering pump. Like maybe your PO. There is a difference.
I was about to say 1.5 inch pipe!!JGW: I think a lot of guys confuse a bilge pump with an emergency de-watering pump. Like maybe your PO. There is a difference.
BTW 3/4" standard hose would have about 3 cups of water (10' of hose) flow backwards. If that causes your bilge pump to cycle, you need a better float/Electric switch.
I had a peanut butter cracker plastic wrapper get into my bilge (aren't grand kids lovable). That small "back flush" kept the wrapper from plugging the pump suction.
BTW my bilge pump hose is <6' long, smooth inside black neoprene hose and NO fittings.
Jim...
I just did the expected head loss on a 600 gph flow in a 3/4" hose, 10 feet long with fresh water with one ball valve , one 90° elbow and above water discharge. Ready for the friction loss or GOLD curve point...
Friction Head loss = 0.2 feet
Add to that the static elevation above pump discharge. Lets say 2 feet for example
you expect total loss is 2.2 feet loss. For salt water multiply by ≈1.03 for heavier density and you get...
2.27 feet TOTAL HEAD LOSS
Find the pump curve shown in the above link for Rule® pumps shown on @Maine Sail post#26 and you will see the actual averge flow you will need and pick a pump.
To get an expected 600 GPH you would need a minimum of 800 gph size and full 12VDC at the pump max flow. I would buy the 1000 gph size for wear, tear, low battery and safety factor to assure 600 gph. I can do precise calculations but notice you still have to pick a standard pump size. This shows the friction loss is normally very small percent of the needed number or ≈12% in the above case.
Jim...
PS: @Maine Sail I think I can make it easy to compensate for better real pump capacity.
I will try to post something soon on friction head loss "made easy".
If in fact the volume of backflow is small I would agree. However, if the volume is enough to restart the pump then you'll end up with that amount of water being pumped repeatedly until, as indicated in another post, the battery goes dead. The solution to avoid a check valve is a good one IF and only if the return flow doesn't restart the pump. If there is enough bilge volume then setting the switch above that level would allow eliminating the check valve.....otherwise it will be needed ....and yes it will be a maintenance item.Well, pump head is elevation and friction loss. Friction Head is the "pack pressure" caused the pump flow and varies with flow rate, pipe diameter, inside smoothness and fittings (like elbow, valves etc). Elevation is a constant, assuming the same liquid properties. Fresh water has less elevation head than salt water.
Time the filling of a gallon container and you get a good idea of the installed pump rate.
Back flow volume is minor and a good thing, to back flush the pump input strainer. Check valves are notorious for failing and reduce the pump flow by additional friction head loss.
Jim...
PS: I am slowly working on "bilge pump" sizing "made easy" post for the forum. My hold up is the "K" friction factors for standard fittings are not readily available.
Mine does have a check valve which has worked flawlessly for many years although I don't know
anything about the likely life of a check valve...I should have my check valve expert look at it in the next week or so.....exp. the filter.
anything about the likely life of a check valve...I should have my check valve expert look at it in the next week or so.....exp. the filter.