How do I delay bilge pump shutoff?

[Jeffrey1950]

……. Or am I overlooking a simpler solution?

I have a manually switched bilge pump deep in the bilge and typically the bilge has a couple of inches of water in it. If I run the bilge pump until it’s sucking air, then turn it off, the bilgewater hose to the stern then empties its contents back into the bilge - that’s the two inches and it’s ok by me - any more than that is delivered out of the stern.

However, I’d like to install a float switch half way up my bilge so that if ever the boat were taking on lots of water it would cut in. As I see it though, the pump would only run until the float switch returned ti its starting position, the water would still be half way up the bilge and the pump would be activated again minutes later.

Is there a timer (perhaps adjustable) which I could fit so that, once activated, the pump would run long enough to empty the bilge?

What do others do? It’s an option, I suppose, to let the pump switch on and off and just accept the fact that it will be doing the same again perhaps minutes later - though each time it would be returning the volume of the long hose to the bilge at each cycle so less efficient at baling out water.

[jt11791]

Few boats, if any, do what you are asking. Just put the switch low in the bilge. If your boat is taking on water having the pump come on frequently, but for a short time, uses the same power as having it come on infrequently, but for a longer time.

Many boats do have a second pump (usually larger) and a second switch mounted up higher for emergency situations.

[Kelkara]

Originally Posted by jt11791

Few boats, if any, do what you are asking. Just put the switch low in the bilge. If your boat is taking on water having the pump come on frequently, but for a short time, uses the same power as having it come on infrequently, but for a longer time.

Many boats do have a second pump (usually larger) and a second switch mounted up higher for emergency situations.

This is what I do, but the problem on my boat (with the bottom of the bilge 5ft below waterline) is the water that drains back when the pump turns off ... it's not enough to cycle the pump in calm conditions, but in a choppy sea it will slosh around and can cycle the switch every few seconds, this doesn't actually remove any extra water but does put an unnecessary drain on the batteries.

What I often do in such situations, is disable the float switch, and have a second float switch higher that is attached to an alarm ... if the alarm goes off then I know I need to pay attention to the bilge and/or find and stop a leak.

Manually holding the pump on for about 30s after it switches off does clear enough water out of the bilge, so I have bought a small timer to do that, but I haven't installed it yet, so can't report on whether it works as desired or not.

[geocav]

put a one way valve in the dish charge hose.

[RaymondR]

The gap between switching off and switching on is known as "hysteresis" and insufficient of it is a common problem with automatic switching systems where it's value is not adjustable.

The solutions tend to be:

(1) Changing the system to one which allows the hysteresis to be adjustable (This tends to be a DIY solution)

(2) Put in a small scavenger pump (This tends to work for the big pump but unless you use a diaphragm pump with inbuilt check valves it just transfers the problem to the small pump)

(3) Put a check valve in the discharge (Not favored because it places a potential obstruction in the discharge line)

I have the same problem and the extant automatic system is not working anyway so it's replacement is on the project list. I will be DIYing a system with two sealed floats (Magnet in the float which triggers a reed switch) and a thing called an SCR connected to the top float switch to latch it on. This series circuit will drive a 100 amp solid state relay (Not that it will need 100 amp but I like a bit of overkill)

I am also thinking of a separate warning system with an audible alarm and strobe light in deck somewhere.

[Peel]

My bilge float switch has two separate activation points. It turns on when the water gets above 2", but doesn't shut off until it's down to 1/2". So a little backflow from the discharge hose won't automatically trigger it to turn on again. If your bilge normally has 2" of water in it that can't be pumped out, just install the float a bit higher up. I think it's made by Whale.

[Wolfe10]

Originally Posted by geocav

put a one way valve in the dish charge hose.

Yup, some boats come from the factory with a check valve in the discharge hose from the bilge pump to address just this issue.


Clean it annually!

[steve77]

When we bought our boat, it had the same problem described by the OP. Here is how we fixed it:

Our bilge pump switch is an electronic switch by Water Witch. It has a nonadjustable timer that allows the pump to run 6 seconds after the switch determines there is no more water. This is to allow the pump to clear the water in the discharge hose.

Aqua Alarm also has a line of bilge pump controls with various timers.

On our boat I installed a small diaphragm Gulper-style bilge pump to allow it to pump all but the last little bit of water out of the bilge. The two larger centrifugal pumps and their standard float switches are located higher in the bilge. The Water Witch pump switch keeps the Gulper pump running long enough to empty all but the last 1/2” of water from the bilge sump.

Cheers!

Steve

[andrzej0nl1ne]

The condition the OP describes is actually 2 problems perhaps require 2 solutions.

Problem 1 is the residue in the hoses drains back once the pump shuts off. Keeping the pump running longer won't solve this problem as the hose residue will remain in the hose till pump shuts and will then drain back. The typical pump lacks the air pressure to vacate the hose riser.

To clear out the bilge of the residue water requires a 2nd pump, can be a small pump, that keeps running once the main pump shuts. The thinner hose on this pump means that the residue water is less than before and thus prevents the main pump cycling.

The challenge is how to turn this pump on when needed and keep it running. There are switches that can be programmed to delay start. If they can be programmed to delay shut off this would solve the original problem.
,

Sent from my SM-N986U using Cruisers Sailing Forum mobile app

[Ballsnall]

Originally Posted by steve77

On our boat I installed a small diaphragm Gulper-style bilge pump to allow it to pump all but the last little bit of water out of the bilge. The two larger centrifugal pumps and their standard float switches are located higher in the bilge. The Water Witch pump switch keeps the Gulper pump running long enough to empty all but the last 1/2” of water from the bilge sump.
Cheers!
Steve

I would agree that installing a small diaphragm pump as a scavenger pump below the bilge pump will minimise the issue. Use a small diameter pump , 1/2" outlet or less would be fine and also add a non return valve to this pump rather the main bilge pump.

[Jeffrey1950]

Thanks to all for these well-considered replies.

I will likely try to fix up a DIY solution using a multifunction relay. I found this on eBay and, once it arrives from China, will set it up on the bench first.

[Rumrace]

A float switch is a requirement in all boats. Power boats have two bilge systems. The motor compartment by build code requires a float. The cabin does not. I gather that’s how some manufacturers dodged the code with sail craft without a real engine room.

[wrwakefield]

For the same reasons, we installed a Whale IC bilge pump for what we label as the 'maintenance bilge pump'. [i.e., primary for keepng the bilge dry, but other, higher volume pumps are installed above it to deal with overload or malfunction.]

The diaphragm pump can be installed above the bilge, and the built in [but not adjustable] time delay takes care of cycling on when the boat is rocking [~9 second on delay] and drains the hose when the pump runs as it runs another ~12 seconds after it senses no more water at the pick-up 'strum box'. It only leaves ~ 3/8- 1/2" of water in the bilge when it shuts off...

Water sensing is electronic [no moving parts.]

This- along with Whale's shower sump replacement equivalent- suit our needs very well.

In case this is of interest.

Cheers! Bill

[thinwater]

Originally Posted by Wolfe10

Yup, some boats come from the factory with a check valve in the discharge hose from the bilge pump to address just this issue.


Clean it annually!

Another risk, for those that winter in the water, is that if the cabin temperature goes below freezing, the check valve will freeze and the pump will be blocked completely. On the other hand, if the water can drain to the bilge, the bilge does not freeze (the hull is above freezing) and the pump will continue to work. A low loop in the hose has the same result. I've seen boats sink because of this.


I'm not a fan of check valves for this.Instead, keep the hose run short, or go high and then let it run down hill to the exit.

[flee27]

Here is a product that can do what you originally asked as far as a timing device to run the bilge pump after a mid level switch cut off. This is not a marine product but can be programmed to preform many timing type function with different types of triggers.

Google "PAC-AUDIO TR-7"

Foster