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Old 27-02-2021, 15:24   #1
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Bilge pump to pump out below waterline

We are rebuilding a racing sailboat into a cruising sailboat. The problem is that it does not have a bilge but rather 21 small compartments, so I have installed numerous of aquarium pump in each separate compartment. In the front of the boat and in the galley it all pumps into the shower pump, which pump it up to the sink hose.

The pumps can be operated manually, but I have a switch located in the room next to the mast, which seems to get filled up first. The question is what to do about the 5 comparantents at the stern, They hardly get any water, but some water do get in every time its raining and you step into the boat. Up to now we manually empty these compartments by pumping the water int a bucket twice a year so its not a big deal, but I would like to install pumps in these compartments as well. Next to the engine bay there is a thru hull which is not in use, its locked off by a ball valve and an endcap. So can I use this one to empty the water , is it enough with adding a check valve or do I need to run a hose well above the waterline? Or is it better to leave it and drill a new hole on the side of the boat?
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Old 27-02-2021, 16:22   #2
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Re: Bilge pump to pump out below waterline

depends on if you are comfortable with your boat floating on that check valve-- no way i would be- that valve fails you have a problem real fast or rather the insurance company now owns another boat. the hose should go well above the water line with a vacumn breaker loop in it anbd exit well above the water line so that it does not go below waterline when boat is heeled over- jmho
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Old 27-02-2021, 16:22   #3
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Re: Bilge pump to pump out below waterline

You can use the existing through hull so long as you run a hose up high with a vent fitting in it.

It would suck in a terrible way to have the boat sink from a tiny little bilge pump.
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Old 27-02-2021, 17:16   #4
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Re: Bilge pump to pump out below waterline

is it impossible to drill limber holes so that the water will all drain into one or two compartments ?

what is the hull material ?

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Old 27-02-2021, 17:40   #5
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Re: Bilge pump to pump out below waterline

Quote:
Originally Posted by chrisr View Post
is it impossible to drill limber holes so that the water will all drain into one or two compartments ?

what is the hull material ?

cheers,
That is the only rational solution.

Parenthetically, who makes a boat with 21 small bilge compartments?
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Old 27-02-2021, 19:35   #6
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Re: Bilge pump to pump out below waterline

I come from a chemical engineering background. Designing and building complex chemical plants. There was one rule that was never violated: Do NOT trust a check valve. NEVER. EVER. No matter how much money it saves, or how much easier it is to use.

There is no check valve in the world you should trust your life to. And if it is keeping the ocean out of your boat, you are trusting your life to it. Just do it right, and pump the bilge out above the waterline! This is no place for shortcuts.

A vented loop is only acceptable if you can be 100% sure that the vent will never clog. 100.00%.

And seriously, 21 bilge isolated compartments???? That just shows a complete lack of understanding of how a boat should work. Repeat after me, "Limber holes are my friends!"
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Old 27-02-2021, 20:44   #7
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Re: Bilge pump to pump out below waterline

Why not fill the compartments with foam up to some common height.
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Old 27-02-2021, 20:47   #8
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Re: Bilge pump to pump out below waterline

We ran our bilge pump lines aft and up since even on a heavy cruising boat sometimes the rail is in the water and any line out midships would be a liability.
Just my 2 cents.
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Old 27-02-2021, 21:22   #9
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Re: Bilge pump to pump out below waterline

Quote:
Originally Posted by skatun View Post
We are rebuilding a racing sailboat into a cruising sailboat. The problem is that it does not have a bilge but rather 21 small compartments, so I have installed numerous of aquarium pump in each separate compartment. In the front of the boat and in the galley it all pumps into the shower pump, which pump it up to the sink hose.

The pumps can be operated manually, but I have a switch located in the room next to the mast, which seems to get filled up first. The question is what to do about the 5 comparantents at the stern, They hardly get any water, but some water do get in every time its raining and you step into the boat. Up to now we manually empty these compartments by pumping the water int a bucket twice a year so its not a big deal, but I would like to install pumps in these compartments as well. Next to the engine bay there is a thru hull which is not in use, its locked off by a ball valve and an endcap. So can I use this one to empty the water , is it enough with adding a check valve or do I need to run a hose well above the waterline? Or is it better to leave it and drill a new hole on the side of the boat?
We have a similar problem: multiple sections in the bilge and water collects in each one even with limber holes.

Our solution was to install a single whale gusher pump, which is self priming, and put a long piece of hose on its intake. The pump exhausts above the waterline (not through a check valve).

So now when we want to pump out the bilge (bilges) we take the long hose and stick it into the bilge sections one by one. Suck a little here, suck a little there. The hose reaches all the way to the bow and stern so those little place in the ends of the boat can also be pumped dry.
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Old 28-02-2021, 02:11   #10
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Re: Bilge pump to pump out below waterline

Quote:
Originally Posted by chrisr View Post
is it impossible to drill limber holes so that the water will all drain into one or two compartments ?

what is the hull material ?

cheers,
Well if you watch Sailife, he had to rebuild all of his structural members due to water inside them, that can easily happen if you drill holes through not solid fiberglass members.

I could of course drill a big hole, fill it with thickened epoxy and then redrill a smaller hole. Problem is then that that new hole is impossible to get flush with the surface and most likely be 5-10mm above it, i.e there will always be a bit of water standing in it, vs my aquarium pumps which almost leave nothing.

I will make a video of the setup next time I go down to the marina.

I might just run a small hose(8mm) all the way to the aft of the boat and empty the bilge above waterline.
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Old 28-02-2021, 12:09   #11
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Re: Bilge pump to pump out below waterline

Quote:
Originally Posted by skatun View Post
We are rebuilding a racing sailboat into a cruising sailboat. The problem is that it does not have a bilge but rather 21 small compartments, so I have installed numerous of aquarium pump in each separate compartment. In the front of the boat and in the galley it all pumps into the shower pump, which pump it up to the sink hose.

The pumps can be operated manually, but I have a switch located in the room next to the mast, which seems to get filled up first. The question is what to do about the 5 comparantents at the stern, They hardly get any water, but some water do get in every time its raining and you step into the boat. Up to now we manually empty these compartments by pumping the water int a bucket twice a year so its not a big deal, but I would like to install pumps in these compartments as well. Next to the engine bay there is a thru hull which is not in use, its locked off by a ball valve and an endcap. So can I use this one to empty the water , is it enough with adding a check valve or do I need to run a hose well above the waterline? Or is it better to leave it and drill a new hole on the side of the boat?
During my boat search I viewed one 40' sailboat that resembled the bilge areas you mentioned but certainly not that many. It was caused by the basically flat floor surface with very shallow bilge areas with pumps located here and there...I couldn't believe there were so many...I didn't buy the boat despite the attractive price.

To me this speaks against those using a boat for something other that for which it was designed, particularly in the extreme as is this case. The many advantages of one use go against the advantages of the other and possibly to the determent of the boat's safety itself.

I have no solution to your issue other than starting over again with a cruising boat to go cruising in.

~ ~ _/) ~ ~ MJH
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Old 28-02-2021, 12:35   #12
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Re: Bilge pump to pump out below waterline

You title the post 'bilge pump' but what you are talking about is 'de-watering' That is taking the last bit of water out of the corners to keep the bilge dry. Always a challenge and often a sponge is the only way. I would second the idea of limber holes. Drill through the stringers as low as you can and then glue in some PVC tubing with epoxy to ensure water can't get into the stringer. The traditional trick for a dry bilge is then to pour in hot pitch until it is level with the limber hole. On a resin boat you could do this with epoxy but do it in layers, if it is to thick it can get very hot when curing - like smocking!



Now bilge pumps. A bulge pump is an emergency pump designed to cope with flooding. It could be you have a sea-cock fail, a seal on the prop shaft or just a large wave that swamps the boat. Whatever the cause you need one main pump and a backup. The main pump should be able to clear water out of the bilge fast enough for you to see whats going on so you can sort out the leak. A good test is to remove the log, which can usually be easily pulled. Your pump should be able to clear water as fast as it comes in. On my boat that is about 2,000 - 2,500gal/hr and having a fairly deep bilge so some lift and about 5ft of hose I find a 4,000gal pump is fine. With a shallow bilge you may get away with 3,000. You can make the capacity up by fitting more than one pump but don't consider anything less than 2,000g/hr they simply don't work. Make sure you also fit hefty wiring and don't run it through a standard bilge control panel, the sort that has 'on, auto, off'. The switches on these will not take the current. If you want auto control fit a min 30amp relay controlled by the switch. This is for short term emergencies. These types of impeller pumps are not designed to run continuously and have a duty cycle around 15-30min depending on quality.
You then need a continuous duty pump of about 1/2 the size. This will probably be a diaphragm pump or a flexible impeller. The intake should be a couple of inches below the intake for the big pump. This is there so that if you do spring a leak and can do a good enough job in slowing it down to save the ship from sinking you have a pump that will keep going long enough for you to get to harbour. The other factor is that if you main bilge pump and its float switch only kicks in with high water and stays dry the rest of the time it will last way longer. Ideally you want a manual pump as well so when the other pumps drain the batteries you don't sink!
Once the big pumps have cleared the main water your de-watering pumps will do the last bit. Big pumps always leave some water because the have big hoses and pickups.
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Old 28-02-2021, 12:38   #13
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Re: Bilge pump to pump out below waterline

Quote:
Originally Posted by MJH View Post
...To me this speaks against those using a boat for something other that for which it was designed, particularly in the extreme as is this case. The many advantages of one use go against the advantages of the other and possibly to the determent of the boat's safety itself...

I have no solution to your issue other than starting over again with a cruising boat to go cruising in.

~ ~ _/) ~ ~ MJH
Sorry, MJH, this is utter nonsense. For any bad attribute that one boat has (for example lack of a proper bilge area) the other boat has its own bad attribute (such as inability to sail upwind), or a myrad of other things.

There is no such thing as a "cruising boat". Any boat used for cruising is a "cruising boat"

Even though it makes pumping the bilge more complicated I am happy that I have a flat bottom in my boat. It reduces wetted surface and improves the effectiveness of the keel. You may disagree that if one intends to go cruising these are important but I am just as much a cruiser as you to to me they are important.

The same goes for many other design and build differences between boats. One person's crumbs are another person's cake.

As for the question asked by the OP, or the person looking at the 40'er above. This is easily solved. We installed a self priming pump with a long hose as a pick up. The hose is coiled near the companionway. It can reach into all areas of the bilge. The pump exits aft into the cockpit drain system.

If water gets into our bilge (2.5 gallons seems like a flood, it comes over the sole when heeled) we turn on the pump and dip the hose into the places where water has collected. It works when you are level, when you are heeled and reaches both the bow and stern.
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Old 28-02-2021, 12:48   #14
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Re: Bilge pump to pump out below waterline

Quote:
Originally Posted by skatun View Post
We are rebuilding a racing sailboat into a cruising sailboat. The problem is that it does not have a bilge but rather 21 small compartments, so I have installed numerous of aquarium pump in each separate compartment. In the front of the boat and in the galley it all pumps into the shower pump, which pump it up to the sink hose.

The pumps can be operated manually, but I have a switch located in the room next to the mast, which seems to get filled up first. The question is what to do about the 5 comparantents at the stern, They hardly get any water, but some water do get in every time its raining and you step into the boat. Up to now we manually empty these compartments by pumping the water int a bucket twice a year so its not a big deal, but I would like to install pumps in these compartments as well. Next to the engine bay there is a thru hull which is not in use, its locked off by a ball valve and an endcap. So can I use this one to empty the water , is it enough with adding a check valve or do I need to run a hose well above the waterline? Or is it better to leave it and drill a new hole on the side of the boat?
Drill a new hole above the WL.
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Old 28-02-2021, 13:27   #15
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Re: Bilge pump to pump out below waterline

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Originally Posted by Lepke View Post
Why not fill the compartments with foam up to some common height.
Like it - or else limber holes.

By the way you might need 1 very big disaster recovery (maybe) bilge pump above all those compartments. It will never get wet so test it manually every now & then...
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