I am going to throw in a dissenting view - I don't automatically believe that one needs
an auto bilge pump. I believe that auto bilge pumps can give a false sense of security
and aren't always suitable to every boat however there are situations that I would recommend them.
Consider the following points.
- Auto systems are designed to cope with slow ongoing leaks while boat is unattended
- Auto pumps rarely cope with a large ingress of water
- Auto pumps only operate as long as there is sufficent power supply available
Taking the last point first
; they are fine if you are normally connected to shore power while boat is unattended
but if not, you have to calculate your available power to run the pump. Being conservative, I would suggest that you derate your nominal house battery capacity to 80 or 85% and that you assume a 80 to 85% charge capacity as being available. Let's say this becomes 68% of your nominal capacity.
your bilge pump current
draw under your normal operating conditions
. Divide this into the derated capacity to give you the number of hours your pumps will run before you have a totally flat house battery.
Now for point 2 above. Measure your pumping capacity
in gallons per minute under real life conditions. Please disregard any marketing
information about your pump. It's real capacity is dependant on the head
it has to pump and the constrictions of the plumbing
that is peculiar to your installation
. It's actual capacity will be a LOT less than the marketing
literature might suggest. Measure it yourself to know for sure.
With the figures calculated as above, you now know how much water your auto system will remove before it stops working and allows the boat to flood.
You may be able to add some extra capacity if you have a good solar panel installation
but unless you have hard data to work with, I suggest you leave that aspect out of the mix.
Looking at point 1 above, where are you going to get a slow leak on your boat?
typically came hand in hand with wooden carvel hulls, poorly maintained stuffing boxes or decks leaks (rainwater ingress); sometimes from poorly maintained seacocks. Fibreglass (or metal / concrete) boats with well maintained shaft seals
and seacocks just don't have slow leaks.
And unless you have massive pumping capacity and a very large house bank (or shore supply), your pumps won't cope with a large leak - say hose broken on an open seacock or siphon vent clogged on head plumbing
Do your own figures, work out your capacity and the maximum time the boat is unattended; work out how many gallons per day that your slow leak has to be less than for your auto system to reliably save your boat and then compare that to the complexity of the auto wiring system and finally make a judgement call as to whether it is a good idea for you
or not. In essence, it comes down to risk management but please don't blindly think that you must
have an auto system and that having it with make you safe
You might have guessed that I have decided not to fit an auto system to my boat - but I am always aware that I must ensure there is almost zero potential for slow leaks in my hull and deck