From the Drawing Board
More words from an interpreter of customers dreams
by John Welsford

The Hand Bilge Pump
Putting the water back where it belongs

We are just about over the summer sailing season as I write, and for the many of us who dont get out so much over the winter there is an opportunity to rectify a whole seasons worth of neglect and abuse of the boats systems.

There may be a little water in the bilge sump, perhaps condensation and a little spray that came aboard through a hatch left slightly open to let some air in. The missing three of spades and a pair of underpants (the activities were NOT connected) have joined the half roll of paper towels that went down the gap at the back of the locker, a whole seasons odds and ends have also ended up in the lowest part of the boat and the whole lot has been sloshed about by a seasons active sailing becoming a noisome sludge that is indigestible by even the most voracious of bilge pumps.

Along comes our hero, the boat is motored over to the haulout with the foul brew lurking under the floorboards making the boat not the nicest of places to be with the hatches shut so our hero forsakes his normal place, posed behind the helm (heroically of course) and heeding his wife’s threats never to go sailing again if the boat smells like that he ventures below to pump the mess out. You must be kidding!!!

Just as well it wasn’t a leak that prompted the attempt to use what is, after all, an emergency device.!

A diaphram pump such as we use is very similar through a wide range of brands, Jabsco, Edison, Vetus and Whale are among the best known but most of them share the basic principals and differ very little one from another and all bar a very few can be stripped fairly easily for service.

Self priming in an installation where the pump is no more than a couple of metres above the inlet , able to move a lot of water in a hurry, ( although there is a saying that the most effective bilge pump of all is a frightened sailor with a bucket) and generally capable of pumping water contaminated with a fair amount of rubbish the diaphram bilge pump is a wonderful device eminently suited to our sport. However the awful slurry that accumulates in some boats, or the mess that is floated by an incoming rush of water from a damaged skin fitting or engine cooling system will choke even the largest mouthed of the type.

Oddly enough the boat with “dusty bilges” is not without risk of bilge pump failure, like anything that does not get used for long periods , when desperately needed it may have become so unaccustomed to work that it may not. Don’t skip the servicing and do check the function with a bucket of water a couple of times a season.

Also a problem in a dry boat is the steady accumulation of tiny odds and ends under the cabin sole. From normal dust and fluff to the occasional (unlit I hope) match dropped when rolling in a seaway these little bits are without peer when it comes to preventing the function of the valves inside the desperately needed pump trying to keep a previously always dry boat afloat. The dry boat, while the most desirable kind, has problems of her own. Make a tidy up down there in the bilges part of the normal housekeeping in any kind of boat.

One hopes never to need the services of your bilge pump, but like other (more expensive) forms of insurance it had better work if you need it. Being a bit “out of sight out of mind “ it pays to check the installation out now and again before Murphy’s Law strikes and you need it with a vengeance.

Note that I said to check the installation out. By that I mean that the pump does not work in splendid isolation, you need to look over the entire system not just the pump. Start with the pickup end of the inlet hose, if allowed to pick up some of that mess I have been on about you wont be pumping, you’ll be swimming.

A “ strum box” is the way to protect the pump from clogging and to be effective it needs to be a big one. Rather like a mesh cage, or a box well perforated with holes , small enough ones to stop anything that might clog the pump, and numerous enough to pass the pumps rated capacity in water even when partly clogged itself. One of my more knowledgeable contacts recommends a surface area in the strum box of at least 20 times the cross section of the inlet hose. Yes, it is big!

Next link in the system is the pickup hose itself, as a suction line this is a vital piece of equipment. Suction will tend to collapse the hose if weak or bent around a tight turn, and any leaks in hose or end fittings will admit air that could render the pump ineffective.

Check the hose for condition and re-route it if necessary to take the kinks out, replace the fittings if they show even the slightest sign of deterioration. Make sure you use stainless steel hose clips or fittings or you will be having to renew them next season, and the one after.

Diaphragm pumps are very simple, there is a pump chamber with one, or two valves to control the water in and out, the chamber has one side made of a flexible material which is moved in and out by the lever on which the operator swings. This makes the chamber larger then smaller, sucking water in through one valve , then forcing it out through the other valve and so overboard. these valves are , together with the diaphragm itself, critical to the operation of the pump. Normally a simple flap they should be very flexible, without any cracking or damage to the seating or valve material, any cupping or curling will prevent the valve from sealing properly so if any of these problems are evident it is a replacement job.

A major wear point of any pump is the diaphragm itself, continually flexed in and out it can eventually crack or split, a few might perish over time so all require careful inspection at regular intervals.

Around the edges the seal between the body of the pump and the diaphragm should be perfect . While the edge seal can be helped with appropriate sealing compound if a persistent leak is evident this is not the ideal repair. Some are gasketed, some are secured by screws and some have a plastic ring that may bulge if over tightened and suck air rather than water. In fact when using metal screw or bolts in plastic components it pays not to do them up too tight in any case. I do use a smear of Anhydrous Lanolin ( wool grease without the smell) on my pump parts but do check that it is compatible with the synthetic rubbers used.

Some of the better pumps have a “door” in the front to allow rapid access and clearance of the valves if blocked so check the gasket and the closing mechanism. If retained by a screw threaded nut or bolt make sure this is free and not immoveable with corrosion. While at it check the interaction of the various metals within the pump, dissimilar metals can suffer from electrolytic corrosion and I have seen alloy bodied pumps bolted down with brass bolts, a sure recipe for disaster!

Mechanically speaking there are very few parts to worry about, two or three pivot pins, all of which should be positively retained ( check the split rings or securing split pins, never use split pins twice.) and not sloppy in their bearings, the handles stowage is also an important part of the pumps functionality so make sure it is going to be “right there “ even after a full rollover.

Mounting the pump correctly is vital., the mounting has to be strong enough to cope with a panicky pumper , the bolts need to be big, well washered, fitted with locknuts and very strong. The pump has to be positioned so that pumping is easy and can be sustained for a long time and last but not least every part of the system needs to be easy to get at to unblock or repair.

Finally, the outlet hose. As this is under pressure it can be a little “sad” and still function but while you are in overhaul mode why not check it for routing, fittings, condition and length. Look hard at the through hull fitting too, you might end up energetically pumping the water back into the boat!

Water and boats have a love hate relationship, Love the stuff outside, hate it inside. Your bilge pump is an essential part of keeping this relationship a livable one so look after that so often neglected pump and never forget that it is part of a system, very simple sure but still, all parts of it have to work.

Who knows from experience how fast a frightened man with a bucket can move water.