Second bilge pump

[Aurelia]

I have space and wiring from my old macerator pump that I would like to reuse for a backup bilge pump under the cockpit on our boat. Could I connect a second similar sized pump to the exising bilge hose and use it as the backup line? Would it need some type of valve on each line to prevent the other from pushing water the wrong way? If I used my abandoned macerator line for the second pump, what type of valve should I use to prevent backflow of water when not in use? (the macerator thru hull is right at the water line and could take in a bit of water if not properly sealed)

[Sea Wolf]

Greg-

Although a lot of interesting and creative systems could be designed using one-way check valves in your situation, the general rule of thumb is to not use check valves in bilge systems because their constricted nature limits the amount of water that can flow through them, and is therefore self-defeating to this emergency type of water removal system. Two pumps + two check valves + one outlet hose may not equal any more output than the system in place (!)

Also, any underwater intake, such as bait tank through-hull, should be carefully monitored. The best solution here for a moored boat, would be to add a ball valve which can be positively closed off when not fishing and the boat is moored, rather than rely on a check value, which can become clogged and leak backwards anyway.

Joe.

[rogerbum]

I'm guessing Thataway Bob will respond but I'd recommend against putting a Y in the system and using check valves. While you can get one-way check valves, they will restrict the flow a little and they are another potential source of failure. Check valves are notorious for failing (often in the open position). I'd recommend that you simply install an extra pump and an additional through hull (well above the water line. The sides of the hull are generally 100% fiberglass and the installation of an additional through hull is pretty easy.

[tomherrick]

Don't know if it'd be called a backup or not, but I've got two bilge pumps: a 750gph for nuisance water with the sensor switch at the bottom of a recess, and a 2000gph with its switch mounted about 3/4-inch higher for more interesting situations. When I reinstall them I may lower the bigger pump sensor switch. Each pump has its own hose with no check valve.

[thataway]

Agree 100% with Roger. I would not use the macerator pump. There is a macerator plate, then a rubber impeller. Most bilge pumps use plastic impellers or bronze impellers. An engine type of water pump which is constantly submerged will use a rubber impeller.

A loop above the waterline will be used rather than a check valve. Don't "Y". Too many problems. The old macerator thru hull, probably would be resolved by glass over or a thru hull fitting put on it.

[Capital Sea]

On a 22 all the water drains to the same place and the boat came equipped with a pump mounted between the tanks and plumbed to a through hull with a backflow preventer.
I wanted to install a backup but did not want another hull penetration. So, I installed the 2nd pump between the tanks and routed the outflow straight up and into the motor well where it drains overboard. The elevation is only 5" or so higher than the water would be pushed if it went to a through hull. I keep a plug in the opening until when the manual pump is needed.
In a crisis I get over twice the flow. I have only used this pump when the primary gets fouled with pine needles or other detritus and this allows me to work in a dry well area. Power supply passes through a fuse with an on off switch in with the battery.
This short and easy project gave me the backup I was looking for prior to heading out to Desolation Sound. I expect a float actuated backup would be a better choice for those who keep their C-dory on the water.

[Aurelia]

Sounds like I could use the old macerator outlet if I put a ball valve on it for safety and used it only in case of primary pump failure which is what I want. I would activate the second pump manually switched and turn the valve for output. Right now I just have that hose capped. I will skip any Y activities as I agree with the logic against it.

Thanks Guys,

Greg

[Aurelia]

Just put in an Atwood 1200 Tsunami bilge pump next to the primary pump as a backup unit. I used the wiring/switch from the macerator and will run it manually if needed for now. It uses the former macerators 1" discharge line and I used a bucket of water to test it out. Pumps strong and the exit is high enough (same as other pump) that I am not worried about installing a ball valve to keep outside water from flowing in through the pump.

There seemed to be water in the line which originally made me think it was near or below the outside water line but I blew it out and found it was just some standing water and nothing to worry about.

I will post a pic soon.

By the way, anyone with a 25 (or any boat) needs to buy one of these or something similar:

http://www.carnivalsource.com/store/p/152516-Water-Toys-Pump-Action-Water-Stick-Each-.html

Cindie got something like this for Aven and it now lives on the boat becuase it is basically a big syringe and will remove the last bit of water from the bilge in two seconds and can then be used as a bilge water gun.

Greg

[tomherrick]