Designing a bilge pump system

You’re bilge pump system has to handle two situations – pumping out the normal drowning-300x247accumulations of water from stern gland, condensation and minor leakage, and pumping out a large influx of water in an emergency.

The most likely causes of a catastrophic leak in a displacement boat are:

  1. The loss of a seacock – either the hose becomes detached or the seacock itself breaks off the through hull.
  2. Loss of a through hull transducer.
  3. A disintegrating drive shaft stuffing box or stern gland.
  4. An overheating engine which melts the exhaust system components and pumps water into the bilge.

Holes in the hull caused by grounding or collision, and flooding by waves could be any size; it’s unrealistic to design for such freak occurrences.

Simple fact: A 1½” hole (such as an open seacock) located 2’ below the waterline will let in around 60 US gallons (230 litres) per minute. That’s 3,600 gallons per hour. That water weighs nearly 30,000 lbs. If you were so inclined you could calculate the amount of water your boat could accommodate before she sank. It isn’t many hours for the size of boat most of us sail.

So, ideally, you need an emergency bilge pump system to handle around 4,000 gallons (15,000 litres) per hour. You also need a supplementary system to keep the bilge dry.

Types of pump and how to drive them.

We can power our bilge pumps in three ways:

Mechanically, off the engine.

Electrically, from the batteries.

Manually, by a crewmember.

Think about these options a little: To drive the pump mechanically the engine must be running; to drive the pump electrically there must be juice in the batteries; to drive the pump manually a crew member must be available.

To cover all contingencies the bilge pump system will need to be a combination of pump types.

Capacity ratings

Now, before we select the appropriate pumps, let’s consider the pump capacity rating. I’m going to try and make this as simple as possible because not everyone wants to plough through charts and graphs and extrapolations to calculate the precise capability of a bilge pump.

An electric pump with a rated capacity of 2,000 gallons per hour will only do this if there is no hose connected and the batteries are bulging with volts. But in real life the pump has to lift the water out of the bilge and push it uphill to a discharge point. Furthermore, it has to push this water through a pipe, and various bends and probably a seacock. This combination of the uphill battle and the resistance in the system is known as the pressure head and it must be applied to the pump’s rated capacity to get the real world capacity.

My rule of thumb for calculating pressure head in a typical 25’ to 45’ boat installation is to measure the height from the pump to the highest point of the pipe run and double this figure to give total pressure head. So, if you want a pump to move 2000 gph vertically 5’ your total pressure head is 10’. Now look at, for instance, a Rule 2000 electric pump which has an open flow rating of 2000gph and apply the 10’ pressure head on the manufacturers chart; you will find that this pump does a little under half of the open flow rating at this pressure head.

So, my second, and simpler, rule of thumb is – down rate electric pump capacity to 40% of rated capacity. And be aware that this requires the batteries to be fully charged; depleted batteries and dodgy wiring will further degrade performance.

Your 2000 gph pump will actually handle around 800 gph.

Mechanical and manual pumps usually give the capacity at a particular pressure head so their selection is less confusing, but the rule about total pressure head stands.

The biggest manual pumps, such as the Edson 30, will pump one gallon per stroke and the Whale Henderson Mark 5 about half that rate. Although some manufacturers give pump capacity at hugely optimistic pumping rates, 70 strokes per minute for instance, in reality 30 strokes per minute is hard work; if you can manage that you’ll get 1800 gallons per hour from the Edson. These are physically large pumps and can be challenging to house on a small boat. Lower capacity pumps take up less room.

Types of pump

Every boat should have at least one manual bilge pump. Manual pumps are diaphragm 23739F-ppumps and the best type are double acting – they pump on both forward and backward strokes of the handle. Think about its location and how easy it will be to operate in an emergency. A long handle that can be operated in a standing position is best; kneeling in the cockpit is less good. Do what you can.

Electric pumps are, most often, of the submersible, centrifugal type. Such a pump would form the basis of your non-emergency maintenance system – to keep your bilge dry under normal conditions. Equipped with a level switch it will cycle on and off as needed to keep nuisance water from building up. Float switches are notoriously unreliable so check them frequently; electronic switches with no moving parts, such as the Water Witch, are usually a better downloadchoice.

You may wish to add a second, higher capacity pump as an emergency pump and it should be designed to come on if the smaller pump isn’t coping. It should have a level switch located higher in the bilge than the maintenance pump. This switch should operate an audio/visual alarm to tell the crew it has operated. You must be able to override the automatic function and force the pump to run if the switch fails.

If your boat can accommodate it the best of all pumps is a mechanical clutch pump, belt driven off the engine. A Jabsco Series 51270 engine driven pump will handle 4,100 gph at 10’ total pressure head but is physically large and nearly impossible to house on smaller boats.

Your engine already has a pump on it, the cooling water pump, and some advocate that this be plumbed in such a way that by switching a valve it will draw its water from the bilge instead of from outside. I’m very sceptical of this advice – the engine pump doesn’t move an awful lot of water, and I’d hate to be jeopardising my engines cooling system when I already have an emergency on my hands.

So, to sum up: A typical bilge water management system will comprise a 12v submersible pump to handle normal seepage, one or two larger electric pumps to handle larger influxes and a manual bilge pump to supplement the electric pumps or replace them when the batteries are flat. An engine driven pump would be a very desirable addition.

Oh, and a baling bucket is a vital component of any leak management system.

Installation considerations.

It will be clear from the discussion of pump capacity that keeping the total pressure head as low as possible is important. The pump in the bilge should be located as close to being vertically in line with the discharge hole as is feasible so that the length of horizontal run is minimised. The maximum lift height will be determined by the distance between the pump outlet and the discharge point, or the top of any loop, vented or otherwise, in the line. Sharp bends should be avoided. The pipe should have smooth interior walls. You’re trying to make it as easy as possibly for the pump to move the water – don’t put obstacles in its way.

You’ll want the bilge pump discharge hose to be well above the heeled waterline. If you can’t achieve this you’ll need to consider a vented loop. Try hard to avoid that need.

Consider installing your electric pumps and their switches on a common base; I use a piece of Plexiglas. If your bilge is very deep you can attach a handle or lanyard to this base plate to allow you to lift the whole assembly within reach for maintenance and repair.

OK, those are my thoughts on bilge pump systems, but let me say right now that I have never had a boat in which the bilge pump system could evacuate 4,000 gph. In smaller boats it’s just impractical to achieve this capacity, as you may have gathered from the above. Top priority, therefore, is to avoid a situation that would require such a capacity:

Prevention and preparation

Minimise the number of holes in your boat. Use a manifold or seachest where appropriate to combine several functions into one seacock. Use suitable seacocks – bronze, stainless or Marelon. Use quality hose and double clamp it. Maintain your seacocks, engine stuffing box and rudder bearings scrupulously and regularly.

You have to be able to get to all your seacocks easily and quickly even when they’re underwater. At each seacock you must have a soft wood or rubber bung of the appropriate size. Tie it to the seacock with a lanyard. Have a contingency plan for stemming the flow from a hull breach, stuffing box failure, displaced rudder or other catastrophe. Keep your cockpit drains clear and, if your boat doesn’t have a bridge deck (companionway sill) keep the lower companionway hatch board in place if there’s a chance of shipping a wave.

It’s a good idea to have an exhaust temperature monitor on your exhaust pipe. A melted exhaust pipe will allow the engine to pump its raw cooling water into the boat. Melting of exhaust components can occur before the normal engine block temperature alarm sounds.

Note: In the forgoing discussion I’ve used US gallons and (litres) because that’s what most pumps are rated in and it saves me making conversions. If you want figures in Imperial gallons multiply the US gallon figure by 0.83 or divide the litre figure by 4.5.

Lightning strike

Three people a year die from being struck by lightning in the UK. For the USA the figure isimages (3) about one hundred. In fact, globally, you have about a one in ten million chance of dying from being struck by lightning. These figures aren’t very impressive when compared to all the other ways you could die, in fact you’re just as likely to die from being hit by a part falling off a plane as you are from being hit by lightning. You can significantly increase your odds of being struck if you live in a hot climate and go boating, but it’s still very unlikely compared to, say, being hit by a rickshaw.

So I suppose I can be considered pretty unlucky to have suffered a direct hit from a lightning bolt whilst on passage on my 42′ sloop Butterfly, even if no one was killed in the event.

All the electronics were fried and the alternator controller burst into flames, starting an engine room fire. Putting out the fire covered the boat’s interior in extinguisher powder.

Taking stock of the damage we were pleased to find nothing of a structural nature; through-hulls intact, wooden masts still in one piece, rigging and chainplates all OK. It was just the electronics that we’d lost. We found a few small bits of the masthead instruments scattered on deck. Everything atop the mast had been blown off.143638336

At the time we were on the Alligator River heading north to Chesapeake Bay via the US east coast Intracoastal Waterway and there wasn’t much around in the way of boat repair facilities. I managed to buy a fishfinder at a small tackle store and with the transducer strapped to a broom handle we were able to make it the hundred or so miles to our destination without running aground.

I don’t like being aboard in thunderstorms, even if the odds of dying from a strike are pretty slim.

Check your spreaders.

Drooping is not usually a good thing. You don’t want drooping bits. You especially don’t The droopwant drooping spreaders. Drooping spreaders are a symptom of a rig in distress, a rig on the road to catastrophic failure.

Perky upward pointing spreaders are what you want. Perky spreaders have tips that bisect the angle of the shrouds that pass over them. In this way the load on the spreader is even and the spreader is disinclined to be pushed up or down, slackening the shroud and threatening the integrity of the whole rig.

Spreaders come in lots of shapes and configurations: The racier boats have spreaders with aerofoil sections, like little aircraft wings, to reduce wind resistance. Cruising boats tend to have longer spreaders to give a broader based rig, sacrificing sheeting angle for better mast support. Old fashioned cruising boats under about 45’ tend to have single spreader rigs, for the sake of simplicity, whilst more modern boats with relatively taller masts adopt multiple spreaders at shorter boat lengths. Spreaders can be fixed at the mast or fully articulating and they come with a variety of methods of attaching the shroud to the spreader tip so it doesn’t jump out. But whatever the spreaders design, droopiness must be avoided at all costs – check your spreaders now!

A word of caution: Once you become an aficionado of the perky spreader your marina dock strolls will take on new meaning, your eye will be inexorably drawn aloft in search of droopers with the attendant risk of an early bath or a broken toe.

Rig tension

Having the correct rig tension is important because a loose rig can impart shock loads to twangshrouds and chainplates as the mast flops from side to side; a too tight rig can cause structural damage.

A well tuned rig will have equally tensioned shrouds so that the boat will perform well on both tacks, the leeward shrouds won’t dangle flaccidly and the forestay won’t sag. She’ll feel right on all points of sail.

You don’t need a tension gauge to set up the rig – there are methods whereby you can measure the change in length of the shrouds and stays as the turnbuckles are tightened, and there’s always the tune your rig like a guitar technique – “Twang! Middle C, that seems about right.” But the Loos tension gauge gives you a quick, accurate, check and that will encourage you to test often, making sure all is well. For racers who set their rigs to suit the prevailing conditions a Loos gauge is an important tool in their race-winning armoury.

For many of the more popular boats there are tuning guides published by the big sail makers and these give Loos tension gauge settings for shrouds and stays.
There are Loos gauges for wire rigging from 2.5mm to 10mm and for rod rigging of all sizes. We stock them all and we regularly check to ensure we’re the lowest cost supplier.

In the articles section of the Saltyjohn website you’ll find more information on using a Loos gauge to set up your rig.Loos PT2M

A tuned rig is a happy rig, so get yourself a Loos tension gauge.

DIY Dinghy Baler

Balers are easy to make, definitely not rocket science, as you can see from the picture.Bailer
I prefer to use milk cartons because the material is relatively soft and conforms to dips and depressions in the fabric base of the dinghy. For a big boat bilge or hard floor dinghy you might choose a fruit juice carton which is made of sturdier material.

Are you ready for heavy weather?

On a small boat in really heavy weather the only thing most of us want to do is lie in our downloadbunk wishing it would all go away. If you’re seasick it must be a hundred times worse. Going on deck to take action to secure the survival of the boat is a frightening proposition. It’s easy at this point to convince yourself that you should wait until it’s a bit calmer before putting in that reef, or dropping the main, or securing the dinghy which is beginning to come loose in its chocks. Of course you can’t succumb to that inner voice; you have to put on the harness and lifejacket, get yourself out into the maelstrom and get the job done.

If you’ve never been there you can’t imagine just how hard it is to operate under the conditions you’re likely to find on deck: The banshee wail in the rigging, the constant deluge of spray and solid water, the violent motion threatening to hurl you overboard.One hand for the boat and one for yourself is the rule, although for much of the time it’s two hands for you and that leaves none for the boat which is why it’s so terribly hard to perform tasks that seemed so simple when it was calm.

This is why my mantra is simplicity in all things. That huge sea anchor with a complex bridle of rope and chain which you bought for just this occasion is going to defeat your attempts to deploy it, unless you have a large, strong and un-seasick crew. Even putting in the third or fourth reef with your single line reefing system with miles and miles of line is going to be a challenge if you’ve left it a bit late. Securing the boom or tying down those spare fuel and water jugs is infinitely easier to accomplish before the heavy stuff arrives.

So, analyse your systems again and ask yourself how easy it’s going to be to get the boat snugged down and safe when the shit hits the fan. Can you get the sail plan sorted quickly and efficiently? Can you heave-to? Can you secure the helm? Is there any chance of items lashed on deck coming loose?

If you plan ahead and prepare the boat for bad weather before it arrives you probably can lay snuggly, and smugly, in your bunk until the storm passes. Assuming your lee cloths are properly designed and tested, of course, and your lockers have good catches and the floorboards are screwed down.

Reflections on a Scottish trip

We’ve just returned from a splendid few days sailing on the west coast of Scotland with our good friends John and Liz aboard their boat, Claymore, based at Ardfern.Reflections

After a night on board we set off from the marina at Ardfern bound for Tayvallich, which we reached after a downwind run on a sparkling sea in twenty knots of breeze and fine sunny weather. In the distance the magnificent Paps of Jura thrust towards the sky.

Sailing 2016

As we were leaving Ardfern the 305 foot, 1500 ton, schooner Eos came in and anchored. This huge boat is the plaything of American billionaire media mogul Barry Diller. She made quite a sight against the rugged pine covered hillside. You sail in good company in these parts; Princess Anne keeps her Rustler 44, Ballochbuie, on a mooring at the marina.

EosHRH small 2

 

 

We had a splendid meal aboard at Tayvallich that night, swinging on a mooring in the small, protected, bay and then set off early the next morning for a brief stop at the tiny port of Craighouse on Jura. Leaving Tayvallich there wasn’t a breath of wind and everything was faithfully reflected in the mirror-calm waters of Loch Sween.Glorious scenery 1

At Craighouse there’s a distillery and a pleasant hotel and we lingered long enough for a cup of coffee in the tearooms by the small jetty before heading back to Ardfern.

And then the long road home after our short but thoroughly enjoyable sojourn in this heavenly place.