Connie,
Welcome to Sailnet! You can make many friends here and find a lot of good information as well, although the Sailnet built-in search capability leaves much to be desired. Your best bet is to use Google, believe it or not! A Google query that looks like this:
site:sailnet.com "2nd bilge pump"
would grab all Sailnet threads with the phrase, 2nd bilge pump, in them.
Now, on to your question. I recommend starting with
this thread. It's an oldie, but it covers the basics rather nicely IMO including wiring.
There are two kinds of electric bilge pumps. The submersible rotary pump is by far the more common. It is an all-in-one solution that sucks from the bottom of the pump into a rotating impeller, which essentially throws the water into the discharge hose via centripetal force. Submersibles are inexpensive, high volume, low pressure pumps. However, their pumping ability degrades quickly with height. The higher they have to pump the discharge water, the more you must de-rate their capacity. Rule, Shurflo, and several other manufacturers makes a ton of quality pumps of this sort.
The other kind is the diaphragm pump, which is a positive displacement pump. They are more expensive but the pump inlet can be at the other end of a long hose. This kind of pump is sometimes mounted in a locker or under a settee with an intake hose that reaches into the bottom of the bilge. The pumping volume is lower but the the capacity reduction from pumping height is pretty small. This kind of pump requires a separate float switch to sense when the bilge requires pumping. Diaphragm pumps work well when you don't have room for a submersible, such as getting the intake into a deep V, or where the bilge is so deep that it is awkward or impossible to get yourself down into it to mount it or work on the pump. David Pascoe published this article a little while back that recommends the Jabsco diaphragm pumps. If you go this route, I recommend you
read the Pascoe article.
As for putting in a second pump, it is a good idea so long as you run a separate discharge hose to a separate outlet (e.g. a through-hull). Putting two pumps on the same hose is just asking for trouble. A clog causes you to lose both pumps, and unless you install check valves (which are prone to clogging and are not recommended in bilge hose by ANYONE) you can create a loop that pumps from the lower pump back to the bilge via back flow into the upper pump (although this is not so for positive displacement pumps). A discharge loop will drain your batteries dead -- and could cause water damage, or even possibly sink your boat when it is unattended, if the leak is bad enough. It's a good idea to put a smaller pump as low as possible with a larger pump farther up in your bilge. Some folks attach an alarm so they know when the upper pump goes off. After all, the upper pump should never run unless the lower pump fails or is overwhelmed by water rushing in.
If you put in a second pump that is of the submersible rotary type, be sure to run a loop of the discharge hose up as high as possible. If you don't have one, you can end up with backflow into your boat when heeled over to the point that your discharge through-hull fitting dips below the water line.
A last word on pump choices -- due to their lower capacity, diaphragm pumps are best suited as a lower pump. I recommend using a submersible rotary pump for your upper pump. I don't know what the bilge size and shape of the Landfall is, but I expect you can find a second pump will fit as it is possible to find a size and shape of submersible pump to fit almost anywhere these days. My final piece of advice: measure twice so you only have to buy once.
Regards,
Tom
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Coconut Connie
