Bilge Pump

[hpeer]

Originally Posted by a64pilot

Every water pump I have except for the airconditioner pump and bilge are diaphram, I assume a diaphragm pump just doesn't move enough water to be a bilge pump, a large one could of course but it would be a big expensive pump I would think.

I would agree, if you are relying on the bilge pump to take out large quantities of water, dewatering. If the pump is there just to catch the drip from the packing I think a diaphragm would suffice.

I don't know what he is attempting to do. Is he is power or sail? Many older sailboats had/have manual diagram pumps for emergency dewatering.

[Terra Nova]

Originally Posted by hpeer

...Some folks have two bilge pumps, a diagram with a check valve on the inlet to get small amounts of water out and leave a dry bilge. Higher up they will have a bigger rotary pump in case the small pump is over come by flow...

Not quite.

A diaphragm pump can be mounted, up high, and still remove virtually all the standing water, through a hose to a remote pickup, as back-flow prevention check valves are an integral part of its design.

Centrifugal/submersible pumps will always back-flow the water that fills the outlet hose, and MUST NOT have a check valve installed. Float switch can be mounted higher.

Originally Posted by hpeer

...I'm pumping water 8'+ vertically, tell me how to do that, while not getting excess backflow, without a check valve.

By using a diaphragm pump.

[Terra Nova]

Diaphragm pump.

[dlymn]

Sorry Terror Nova but here goes. The main bilge pump needs to be a high volume pump. It has to cope with a bad case situation (don't even think about worst case). The small diaphragm pumps just don't pump enough. I like the idea of a diaphragm and gear/rotary pump combination. The diaphragm sweeps up the drips and the rotary handles the big leaks.

Most pumps are OK unless they are overloaded or overworked. Keep the bilge clean and free of objects that might jam the rotary pump. A diaphragm pump and filter as an ancillary to a rotary will improve the chances of catching the trash before it gets to the rotary. If your pump is operating frequently then look to the leak before you lay the blame on the pump. Most fibreglass boat are fairly watertight except where you have cut a hole to let water in or our. Check all thru hulls. Check your motor cooling system. Check your Hot water service (my pressure valve leaked into the bilge until I flushed out the crap in it ) check your anti siphon drains which often lead into the bilge. Modern stuffing boxes should barely leak at all. Stop water getting into the bilge and your pump-out motor problems will clearly be greatly reduced. Wooden boat? best of luck.

A diaphragm pump is great for the shower pump, but as I said, I prefer to filter out the trash before it gets to the pump to minimize possible damage. Human hair is a nasty clogger of everything and I'm sure that it breeds in the pipes.

We keep the shower system clean with a regular teaspoon of chlorine and only use liquid soap as it doesn't build up gunk in pipes nor does it leave a film over all surfaces.

[Terra Nova]

Originally Posted by dlymn

...The main bilge pump needs to be a high volume pump. It has to cope with a bad case situation (don't even think about worst case). The small diaphragm pumps just don't pump enough. I like the idea of a diaphragm and gear/rotary pump combination. The diaphragm sweeps up the drips and the rotary handles the big leaks...

That's it. On any yacht system as important as bilge pumping, you must have a redundant system--TWO electric pumps or more--a high volume centrifugal pump, for serious inflow, and a diaphragm pump to dry the bilge. Both on automatic float switches, but at different levels, so the high volume pump comes on only if the diaphragm pump cannot handle the volume, and does not short cycle due to back-flow.

[IslandHopper]

Originally Posted by Terra Nova

Diaphragm pump.

They used to be a pretty good pump, fully serviceable, unfortunately no longer available....

[CarinaPDX]

I am always leery of absolute statements, and the "never use check valves" definitely ticks that box. I have used a check valve on my centrifugal bilge pump for 34 years with no difficulties at all. I must not be alone as bilge strainers often incorporate check valves. When installing a centrifugal pump in a deep but small bilge it is often necessary to put a check valve in line immediately after the pump to prevent the water from flowing back and restarting the pump. Since there is a strainer before the pump, and the pump output flushes out the check valve, it is simply not a problem. I also have check valves on the strainers for both 1-1/2" manual pumps; without the check valves the water flows back into the bilge between pumping sessions requiring more pumping. IIRC all of my check valves are chokers, not flaps, which may contribute to their reliability. As I said, never a problem for 34 years, and I have not been good at keeping the bilge cleaned out either. Also, my electric pump is the same Rule for all those years so I guess someone must have spread some fairy dust on my boat.

I agree with the concept of a small bilge pump for everyday use and a larger one for emergencies mounted a bit higher. I have been carrying a 1-1/2" Rule set up with hose and quick electrical connector for emergencies but will be permanently installing it in the near future.

Diaphragm pumps are really low volume, so must have a large centrifugal as backup. The best pump I have found is a Whale Gulper. It is intended for gray water. I use it to pump out the galley sinks (my lead mine sits too low for the sinks to drain overboard). I have been using it for about 15 years and it has never failed. I did rebuild it once but I don't think it was even necessary. It is a keeper.

Greg

[Terra Nova]

Originally Posted by CarinaPDX

...I have used a check valve on my centrifugal bilge pump for 34 years with no difficulties at all...

You've been doing it wrong.

You're not alone. It is a common amateur mistake.

[CarinaPDX]

Really?

The boat has been in the water for 34 years, I have lived aboard for 22 years, and cruised for 17 years, and the bilge pump system has never had a problem of any sort. What is your metric for "mistake"? I'd say it was a perfect installation.

And don't be too hard on us "amateurs". With an engineering degree and having built my own boat, plus all of the time aboard, I have found precious few "professionals" that are as knowledgeable (but most of them, and a fair few knowledgeable "amateurs", are right here on CF - which is why it is always risky to pontificate here ).

Bedtime...

Greg

[Old Snipe]

Common sense tells me that any through hull discharge near the waterline would have a check valve. I cannot imagine anyone thinking otherwise.

[GordMay]

Originally Posted by Old Snipe

Common sense tells me that any through hull discharge near the waterline would have a check valve. I cannot imagine anyone thinking otherwise.

The anti-siphon loop protects against backflow.

[cal40john]

Originally Posted by Terra Nova

You've been doing it wrong.

You're not alone. It is a common amateur mistake.

I guess you better not buy a Johnson pump or call them and tell them of their amateur mistake as some of their centrifugal bilge pumps come with a check valve installed.

Rule specifically states no check valves in their manuals.

I believe the issue is if you have air trapped in the pump at the impeller it could possibly not develop enough pressure to overcome the head of the water downstream of the check valve. I assume Johnson's design has a way to bleed the air out of the impeller not unlike self priming trash pumps.

[Old Snipe]

Originally Posted by GordMay

The anti-siphon loop protects against backflow.

Yes..... a must have when you have enough room inside the hull above the waterline, but I have been on too many boats where it wouldn't take much listing to render them useless.

[a64pilot]

Originally Posted by hpeer

Many older sailboats had/have manual diagram pumps for emergency dewatering.

Is it just the older boats, new ones don't? I would think any mono with tons of weight hanging off the keel would have a manual back up pump?

[hpeer]

Obviously we all need to buy brand new boats every time ther is a change in any of the codes as it is just DANGEROUS, SUICIDAL to own a boat that is not adherent to the latest code. Scrap all the old boats, put 'em down, they are death traps.

We must listen to our handlers.

one of my favorites is that all wire MUST be copper tinned, except on Yanmar engine control cables. They are just plain ol copper.

So all boats with Yanmars must go.