Adding a second bilge pump

[njlarry]

I'd like to add a second higher capacity bilge pump without adding another thru hull. Does anyone have any suggestions on how I can connect to the existing primary bilge hose without one pump discharging thru the other?
Thanks for any suggestions.

 

[kappykaplan]

Don't combine the outputs of the two pumps. You're better off with a second, dedicated through hull for the new bilige pump.

 

[31seahorse]

Hello njlarry,

We owned an Oday 34 and enjoyed sailing her on the upper Chesapeake Bay. I know the logic behind avoiding the "excitement" of drilling extra holes in the hull. Each of the existing thru hull fittings has an important function and usually a dedicated one.

First, you would need to choose a thru hull that is above the waterline.....scupper line thru hull would be large enough to handle the water pumped out, but it could also route water from the cockpit INTO your bilge during heavy rain or other "water in the cockpit situations". I think we can agree that would be a condition to avoid!

You could, perhaps, use an opening that is for discharge water for your air conditioner (if you have one). I'm sure there are a few reasons to avoid that choice too.....for instance, it is probably fairly small diameter and when the air conditioner is pumping water it might go to the bilge also.

But, with the air conditioner discharge thru hull in mind.... We added air conditioning to our boat. By going up the hull to a place ABOVE the interior liner we found a location that was accessable and there was only the need to drill through the thickness of the hull. That location was in the hanging locker. We chose to put our exit fitting just above the liner, but there would be no reason that I remember that we could not have gone higher toward the hull/deck joint. (Our choice was to limit the waterfall sound the neighbors would hear as water come out of the discharge when our air conditioner was running.) Higher would be better for the bilge pump discharge, I think. Decent room to work within the hanging locker, and room for a loop in the line with places to attach it with zip ties or whatever securing method you choose.

After carefully considering the spot to drill the most worrisome point was when I actually pulled the trigger on the drill! A nicely installed thru hull fitting would not detract from the look of the boat. If my memory is correct I drilled a very small centering hole first from the inside out. Then drilled the actual size hole I needed from the outside to limit gel coat damage.

Best Wishes

 

[rgranger]

I'd like to add a second higher capacity bilge pump without adding another thru hull. Does anyone have any suggestions on how I can connect to the existing primary bilge hose without one pump discharging thru the other?
Thanks for any suggestions.

About a year ago, I was shopping on eBay for some through hulls and ran across a bid for a batch of about 20 (all tied up on a piece of string). Some marina was going out of business. I low-balled a bid of $25 and to my surprise I won. I've used the two I needed and still have a string of about 18 through hulls.

If you need one, send the I.D. of the hose and I'll see if I have one of those on the stringer.

It will be yours for postage.

A through hull at the transom is a good way to go and if you put a piece of masking tape over the spot first, you will avoid chipping the gel coat.

 

[Bill1565]

I'd like to add a second higher capacity bilge pump without adding another thru hull. Does anyone have any suggestions on how I can connect to the existing primary bilge hose without one pump discharging thru the other? Thanks for any suggestions.

You wiil need a larger hose to discharge the higher capacity pump.

 

[capta]

You will need a dedicated thru hull, above the waterline with a loop to the deck height and a vented loop. The exhaust line must be appropriately sized for the pump or you reduce the water flow which would be rather counter productive.
There is absolutely no reason not to do this correctly. Just go with the installation instructions that come with the pump; that's why they include them with the pump.

 

[Gunni]

No thru-hulls, 30GPM, no electricity. The ultimate backup bilge pump.

 

[rgranger]

You will need a .... and a vented loop.

Are you sure about the vented loop? What are you venting?

I replaced an old bilge pump just last month and the instructions just said that the line should have a stead incline with no low points or sharp bends. A loop would (by definition) have a low point.

 

[Ron20324]

I replaced an old bilge pump just last month and the instructions just said that the line should have a stead incline with no low points or sharp bends. A loop would (by definition) have a low point.

You're thinking of "droop", not "loop". No, by definition, venting- in this case- would prevent sea water from flowing downhill into the bilge. Unless your thru-hull is really high off the water, there is a chance of back-flow, and flooding, and sinking, das boot..

 

[capta]

You're thinking of "droop", not "loop". No, by definition, venting- in this case- would prevent sea water from flowing downhill into the bilge. Unless your thru-hull is really high off the water, there is a chance of back-flow, and flooding, and sinking, das boot..

Yep, you've got it. A large loop and the vent prevent water from siphoning back into the boat.

 

[rgranger]

You're thinking of "droop", not "loop". No, by definition, venting- in this case- would prevent sea water from flowing downhill into the bilge. Unless your thru-hull is really high off the water, there is a chance of back-flow, and flooding, and sinking, das boot..

Ahhh!

 

[Benny17441]

Well what we may want and what it is sensibly attainable may not be the same thing. The proper way of doing it is to add a second discharge hose with its own thru-hull. The use of check valves and loops are not the safest alternatives to deal with the issue. Consider that a bilge pump is a mere convenience item designed to remove small amounts of water so you do not have to do it manually and by adding an automatic switch it can do its work even when you are away. Unfortunately as a safety item the bilge pump has serious limitations with capacity. The addition of a second pump does enhance capacity if you increase the discharge outlet capacity but they will still be insufficient to handle any significant water intrusion. My point is do understand that adding a second pump does not really provide any significant safety concerns. It just serves a s a backup to conveniently dispose of small amounts of collected water. Two pumps running simultaneously will use double the power and consume the battery capacity faster unless hooked up to shore power. Please understand that I do consider adding a backup pump to be a good idea on a boat left unattended for some period of time but if you are going to do it , do it right with a second discharge outlet.