Bilge switches and sizing

[Skipper Lee]

I wonder what would be considered a typical bilge pump size (GPH) for a 27 Ft fiberglass sailboat.
When I bought this boat I found a new 1250 GPH pump in a locker and the boat has a 500 GPM mounted now which worked when tested.
I thought I might as well change to the larger one but now thinking of installing the new one as well as leaving the 500 GPH in place. I could mount the 1250 higher in the bilge so it would be a just in case pump...
I also found two new switches one float type and an electronic type with two prongs presumably connecting when submerged.
Which switch would you use on which pump?

[Tayana42]

Lee, I’m a little confused about the size of your bilge pumps is it GPH or GPM? 500 GPM equals 3000 GPH.

[fcallard]

Originally Posted by Tayana42

Lee, I’m a little confused about the size of your bilge pumps is it GPH or GPM? 500 GPM equals 3000 GPH.

Someone is confused: 500 GPM is actually 30,000 GPH. But anyway, bilge pumps tend to be rated in GPH.

Furthermore, the actual output of a bilge pump depends on the output hose diameter and length and, importantly, the lift. They don't ever come close to delivering the specified output in the real world. You might also consider that elbows and backflow preventers will also reduce the output.

[Tayana42]

fcallard, thanks for correcting my math. Must have isolation brain.

[Skipper Lee]

Hi and apologies for the brain fart.
Both are GPH.
The 500 GPH (Rule brand) is mounted and works fine as I pressure washed the entire boat out when bought it and the 500 GPH had no trouble keeping up with dispatching the water. The float switch looks a bit crusty and the wiring has hardened as well as has been routed in such a way that it must have been submerged at some times unless it was never wet and that is unlikely.
I suppose I should have asked if anyone is familiar with the Bilge Buddy (electronic switch if that's what it truly is called) that I found with the new Float switch. Is that type is better than the float type?
I suppose the 500 GPH will stay put with new wiring to the switch (whichever of the 2 switches I use) and the new 1250 GPH will get mounted a bit higher and I would use the other new switch that I found.
Then if the 500 can't keep up then the 1250 would start pumping as well.
I have never had a switch other than the float type and am wondering if the Bilge buddy types are good or better than a float type or entirely crap.
I also wonder what size of bilge pump generally speaking would have came with a boat about 27 Ft from the factory. as the boat is from 1978 so I doubt its still original, But I suppose it could be if it wasn't a leaky boat.
I wonder how much water in GPH would enter the bilge if say a 1 inch thru hull valve broke off,
I guess that would be the short answer of what needs to be installed but that would be a big number.

[CarlF]

I have two pumps mounted just as you plan.

Be sure to run a new hose for the 2nd pump. Use at least 1" hose for the bigger pump. 3/4" hose can only move about 500GPH regardless of what the pump label says.

An advantage is that both the pump and the switch of the higher pump will be normally dry. This will make them last much longer. Many cheap float switches (like Rule) fail in less than a year if they sit in water.

[chris mac]

My primary bilge is a diaphragm pump connected to a water witch sensor( metal probes for sensing water height) it seems to work well so far.
But I do have a high volume rotary pump back up on a traditional float switch, mounted slightly higher.
Redundancy is a great thing if you have the room to do it

[CarlF]

I have two pumps mounted just as you plan.

Be sure to run a new hose for the 2nd pump. Use at least 1" hose for the bigger pump. 3/4" hose can only move about 500GPH regardless of what the pump label says.

Both the pump and the switch of the higher pump will be normally dry. This will make them last much longer. Rule float switches (like you have in your picture) have an especially bad reputation for failing early (in as little as a year) if they are always in water. But they still are the most common switch. So I guess I'd use it in the upper bilge pump. I don't know the other switch brand.

When you splice the wires secure the splices as high above the bilge water as you can. At least 12". Insulation nicks or splices in bilge pump wire that sit in water are one of the most common causes of stray current corrosions that can corrode your bronze seacocks and propeller very quickly. Tape is not enough protection. While your at it, check the existing pump wires for any signs of nicks or wear in the insulation.

I'd wire your new pump without a manual on-off switch. Just have the float switch turn it on. This will make the wiring easier. Wire it so that turning off the main battery switch does not turn off the pump. Wire it directly to the battery (with a fuse of course)

[fcallard]

I have switched (pun intended) from mechanical action float switches to Johnson Ultima electronic switched after some failures of both the pneumatic and mechanical types on the two boats I have owned for 25+ years. The Johnson Ultima switches allow an easy check on function by placing 2 fingers on the raised areas on the switch face.

[Skipper Lee]

Chris,
Go Oilers (someday)and hello from Leduc!

That water witch looks like the same technology as the Bilge buddy.
As the float switches don't last that long I should consider using the float type on the secondary/higher mounted 1250 pump and the bilge buddy on the primary/lower 500 pump. Also for your 42 Ft how much pumping ability have you got in place? In each hull to be more precise!
I had a Wharram 40 Ft Narai in the 80's but can't remember what pumping capacity it had.
Let me know if/when you need crew on that nice Lagoon(I just googled them), I'm pretty much always available and sailed around quite a bit on the West Coast if that's where it is.

[fcallard]

Originally Posted by Tayana42

fcallard, thanks for correcting my math. Must have isolation brain.

Those of us who grew up with slide rules had to keep track of decimal points in our calculations. We otherwise could be off by well over a factor of 10.

It can be a useful skill when dealing with folks who use calculators, but pushed the wrong button.

[Skipper Lee]

Both pumps have a pre-determined hose outlet size, do you all recommend upsizing it with a short as possible hose then a fitting to a bigger diameter hose?

[Skipper Lee]

Also,
I hate the thought of putting 3-4 screws each into the hull to fix the them and the switches in place, Is it ok to short screw into the hull? The PO just left the 500 GPH holding on by the hose no screws! I wont be replicating that scenario but thought about gluing a pad in place to screw it to with 5200 or similar.

[chris mac]

Originally Posted by Skipper Lee

Chris,
Go Oilers (someday)and hello from Leduc!

That water witch looks like the same technology as the Bilge buddy.
As the float switches don't last that long I should consider using the float type on the secondary/higher mounted 1250 pump and the bilge buddy on the primary/lower 500 pump. Also for your 42 Ft how much pumping ability have you got in place? In each hull to be more precise!
I had a Wharram 40 Ft Narai in the 80's but can't remember what pumping capacity it had.
Let me know if/when you need crew on that nice Lagoon(I just googled them), I'm pretty much always available and sailed around quite a bit on the West Coast if that's where it is.

In each hull, my primary diaphragm pump is 220gph. Low volume, but filter less and removed from the bilge, so last a long time. I actually replaced the originals(from 93) when I bought the boat last year. Secondary is 1000 gph in one and 1200 gph in the other. I also have a 3rd as a fail safe at 500gph
The water witch has only just been installed, replacing a standard float that stopped working a couple weeks ago.
Leduc huh? That's too funny. I grew up in thorsby, moved to leduc in the early 90's, then out to stony plain to raise my family. I still have family in leduc though!
We are floating around in the bahamas right now, west coast canada is still too cold for me! I'm done with that whole winter thing[emoji39]

[chris mac]

For screws, clean the bilge out squeaky clean, acetone wipe. Then glue in a piece of PVC panel, or plastic board. Screw to that. In a pinch, PVC moulding from home Reno store will work. Use a marine adhesive like 4200.