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Old 18-04-2013, 06:10   #1
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Cycling Bilge Pump

I'm sure this must be at least a bit common - the water left in the pipe above a bilge pump drains back into the bilge raising the water level enough to activate the float switch again. And again and again..

A latching relay looks like it should get around this, with 2 sensors - trigger & reset in this image with another relay as a device to power the pump.



But what to use as sensors, I've never been too keen on float switches, or anything mechanical down there - any suggestions of alternative sensors to detect the water level in the bilge?
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Old 18-04-2013, 06:16   #2
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Re: Cycling bilge pump

That isn't a very friendly environment to locate the relays. A far more reliable method is simply to route the discharge hose in such a way that an inverted loop is close to the pump
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Old 18-04-2013, 06:17   #3
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Re: Cycling bilge pump

There are low cost water sensors for house/commercial alarm systems that are solid state. I bought one to use as a high-water alarm.
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Old 18-04-2013, 06:32   #4
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Re: Cycling bilge pump

Use a small (400 gph) diaphragm bilge pump, with it’s intake strainer mounted low in the sump, and a higher capacity emergency pump mounted slightly higher in the bilge.
The small pump deals with minor rain and shaft-gland leakage (keeping the bilge dry), whereas the larger pump “stands by” to deal with more serious emergency situations (keeping the boat afloat).
Slightly reduce the size of the smaller pump discharge hose, to minimise routine backflow (without compromising ultimate safety).
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Old 18-04-2013, 06:41   #5
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Re: Cycling bilge pump

Conachair,

We found an easy solution to this problem...

We had exactly the same problem. Five times per night the bilge pump came on. Lots of concerns over possible leaks, taste tests whether it is salty or sweet etc - you get the drift.

The solution was easy and permanent. Whenever we have water entering the bilge, we lift the float afterwards long enough for the pump to drain the bilge to way below the level of the float. It's been quiet since, and no installation was necessary.

Oliver
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Old 18-04-2013, 06:46   #6
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Re: Cycling bilge pump

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Originally Posted by S/V Illusion View Post
That isn't a very friendly environment to locate the relays. A far more reliable method is simply to route the discharge hose in such a way that an inverted loop is close to the pump
The relays can be in a nice dry safe box somewhere with tinned wire down to the sensors. An inverted loop won't help - too far below the water line.

Another pump seems an awful lot of work, the main bilge pump almost never runs, steel boat so rain stays outside and ptfe packing means virtually no drips from the shaft.

Off to google for solid state liquid sensors..
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Old 18-04-2013, 06:53   #7
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Re: Cycling bilge pump

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Originally Posted by conachair View Post
I'm sure this must be at least a bit common - the water left in the pipe above a bilge pump drains back into the bilge raising the water level enough to activate the float switch again. And again and again..
If you have a separate float switch, mount it on a block of wood rather than at the bottom of the bilge. If the pump has a built-in float, then it must be mounted a bit higher. Figure the correct position by observing the level of the water when the pump is activated. Because of the height of the discharge hose, there will always be some water in the bilge, unless you put a check valve, which is not recommended and against ABYC's.
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Old 18-04-2013, 06:54   #8
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Re: Cycling bilge pump

i had the same problem. deep sump, long uphill run to overboard drain. i solved it in a not so good way. i installed a one way valve in the discharge line. it stopped the problem but of course it has it's own problem of possibly getting clogged. so far so good.

i think a better answer would have been to put a loop in the line as s/v illusion suggests. but i don't think i have enough height in the bilge to make a high enough loop.
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Old 18-04-2013, 07:13   #9
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Re: Cycling bilge pump

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Originally Posted by GordMay View Post
Use a small (400 gph) diaphragm bilge pump, with it’s intake strainer mounted low in the sump, and a higher capacity emergency pump mounted slightly higher in the bilge...
See also David Pascoe’s article ➥ Boats, Yachts: All About Bilge Pumps - Those Essential Devices for Keeping Your Boat Off the Bottom
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Old 18-04-2013, 11:15   #10
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Re: Cycling bilge pump

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Conachair,

We found an easy solution to this problem...

We had exactly the same problem. Five times per night the bilge pump came on. Lots of concerns over possible leaks, taste tests whether it is salty or sweet etc - you get the drift.

The solution was easy and permanent. Whenever we have water entering the bilge, we lift the float afterwards long enough for the pump to drain the bilge to way below the level of the float. It's been quiet since, and no installation was necessary.

Oliver
Sounds like it would work but float switch is combined with the pump so not poss.

Goggle not coming up with much in the way of sensors, wouldn't it be easy enough to make a couple with some gold terminals and a transistor? Would the water have enough conductivity? Not likely to be all that clean on a old steel boat.
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Old 18-04-2013, 11:30   #11
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Re: Cycling bilge pump

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Originally Posted by onestepcsy37 View Post
i had the same problem. deep sump, long uphill run to overboard drain. i solved it in a not so good way. i installed a one way valve in the discharge line. it stopped the problem but of course it has it's own problem of possibly getting clogged. so far so good.

i think a better answer would have been to put a loop in the line as s/v illusion suggests. but i don't think i have enough height in the bilge to make a high enough loop.
The check valve is not such a good idea if you have a vane pump like a Rule. The water in the line past the check valve means that the pump has to overcome that static pressure when it starts. When the boat heels over you can get some air in the pump, and it will spin but not pump. I had a shower sump pump configured like this, and would have to burp the air out after we went sailing.

Much better to use a diaphragm bilge pump like Gord suggests, as it has not one but two check valves built in.
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Old 18-04-2013, 13:34   #12
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Re: Cycling bilge pump

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Originally Posted by conachair View Post
Goggle not coming up with much in the way of sensors, wouldn't it be easy enough to make a couple with some gold terminals and a transistor? Would the water have enough conductivity? Not likely to be all that clean on a old steel boat.
Hmm, maybe not, more than one connection to batt neg immersed in bilge water.
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Old 18-04-2013, 13:50   #13
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Re: Cycling Bilge Pump

Get a Johnson delay switch.

b.
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Old 18-04-2013, 14:23   #14
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Re: Cycling Bilge Pump

get a new float switch with a longer throw so it will have a bigger difference between on/off
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Old 18-04-2013, 15:16   #15
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Re: Cycling Bilge Pump

donradcliffe - i have a deep bilge.

my electric bilge pump is mounted about 6 inches above the bottom of the bilge. my manual bilge pump (whale titan) is mounted in the cockpit but the pickup is at the very bottom of the bilge.

so my usual routine is to manually pump out the bilge every day. most times there's nothing to pump but occasionally after a heavy rain i'll get a few inches. the electric bilge pump (rule 1800 with separate float switch) only comes on if i'm not on the boat for a few days during a heavy rain. or when i put water in the bilge to test it.

so far everything is working well but i think i'll try to recreate the condition you mentioned to see what happens. i've always worried about that check valve but so far it hasn't created any problems for me....
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