I intend to put a huge ( 3500gph) bilge midships in my 69 42'. I would rather not make an 1 1/2' thru hull to accommodate it and a reducer to an existing smaller one would defeat the purpose. Could I Y at the sink grey water 1 1/2' discharge and add the bilge discharge? This "emergency" pump will be 6-7" above maintenance pump level. So it should never go on ...right ;)
If it does maybe it might squirt out the sink drain? If that happens I have more things to worry about than a wet kitchen rug! And a heads up that bilge systems have gone to defcon-5 isn't an bad thing.
Am I missing anything here or is this a no brainer...?
this inline to stop backflow up to the sink?
You will need to install a check valve in both lines upstream of the Y. This will prevent water from the sink from ending up in the bilge, and water from the pump coming out the sink drain. Local plumbing supply should be able to help with proper size.
Just drill the hole. Once you’ve done it you’ll feel alot less worried drilling more.
I agree with Mike, drill a separate discharge for the serious bilge pump. Any y's, check valves, or stuff like that is going to decrease the real world output of that pump. I had a serious monster pump in our 38 and it had an unimpeded 1 1/2" run about 8 feet to it's own 1 1/2" discharge. I would test the boats pumping systems in the spring by throwing 2 wide open dock hoses in the bilge. My pumps, including "Mongo", could keep up with this inflow. If you're gonna install a "Mongo", give it the best chance to hit it's rated output, and Y's & check valves are not best chance.
My OMGWe're sinking option is a 3500gph sump pump with overboard hose, a re-purposed swimming pool hose. It is a Winter only option but it has been used in anger once for a neighbor's perforated steel hull during the Summer.
I don't understand the reasoning for being that far above the other pumps, if they can't keep up they need help and an alarm should be sounding. An alarm system calling help is probably much more valuable than the pump. One of the members in our harbor has a fully geeked boat that would let him know it was in need of various types of attention so a come save me I'm sinking alarm is within the limits of this topic and may be within the cost parameters as well. The only boats I am aware of (2) sinking had adequate pumps but were not winterized and sank due to compromised through hull fittings.
A local member with a 45 that has done the loop had a catastrophic bow puncture and was able to first make a port, make emergency staunching of leaks then make way to a haul out facility, no special pumps. If you're not on hand there may not be any pump large enough to resolve the problem, 1800insurance works for me.
OTOH the Curmudgeon has a lot of experience of his own and observations of others.
In the interest of confusion,
the OMG pump will be set as a backup
at whatever level doesnt dont allow it to be trigger either underway or at the docknfor day
to day bilge maintenance. What ever level that may be...
As an option for an underway hull breach, I have diverter valves on my raw water intakes, flip the valve and close the sea cock and a 7.4 crusader becomes a bilge pump. Just make sure to monitor the water level as this will move a lot of water in a hurry. Wanderer has 4 2000 GPH pumps installed to work on float switches or manual switches, and I carry 2 3500,s, 1 12 volt and 1 110 volt with 30' of 1 1/2 inch roll flat hose. These are both automatic. The 110 pump has gotten a lot of use pumping out dinghies after a nice refreshing New England down pour. (With a shorter hose)
If your really worried about water intrusion. You can get a bilge alarm that will send a signal to your smartphone. Last time I checked it was a little too pricey for me, almost $1000. But if it helps you sleep at night.
I don’t have a huge bilge pump, but I do have a high water alarm. The insurance company required it. It’s in the keel a few inches above the bilge pump. It’s high enough to prevent false warnings when the water the pupms can’t get out sloshes around, but low enough to know before it’s too late. It’s just a basic float switch wired to a buzzer, I’ve thought about wiring it up to the horn some how for when I’m away from the boat. I also like the idea of using the engines as emergency pumps.
When I bought the boat it only had 1 pump, I installed a second and drilled the through hull near the original, Stainless through hull.
As has been said above, I would not put a Y and the required valves in a bilge pump hose, too much to go wrong.
I have also read a suggestion of not fusing your pumps. I'm not sure how I feel about that, could be an electrical hazard. Maybe just the last ditch pump to ensure it never turns off just because it's working hard.
I'd also recommend checking the size of the wire feeding the pump and ensure there is not much voltage drop, maybe 3-5%. Lower voltage will just pump less water. I've got to think there are a lot of newly installed more powerful pumps on existing wiring and fusing that were designed for the original, smaller pump.
Our secondary pump is a 3700 GPH Rule, with an Ultra Safety Switch, which includes a high water alarm. The switches are expensive, but are supposed to be very reliable for many, many years. A great pump is much less useful if the float doesn't work.
Of course it's not installed yet, first thing this spring. For the through hull, we got lucky, the boat came with 2x 1.5" sink drains and we only needed one in the new kitchen. Last year we only had a 4.5GPH single chamber pump - not so good in an emergency! The plan is to add another pump mid ships and see if I can bring the one in the stern of the boat back to life. That'll make 4.
We also carry one of these on board to plug many different hole sizes (assuming you can locate it):
I would love to add a by-pass valve to at least one of my engines, that would be the ultimate in safety for long crossings.
Those are excellent points Dick.
My question is how much water will come in through say a 6”x6” hole? That’s about the size I would expect if say a rudder was ripped out as happened to someone on lk St Clair last year. That’s the point of these big pumps right? Hit a dead head, rip out a shaft log etc.