Bilge Pump Installation Question

[aussi]

Hi all,

I am planning an electric bilge pump installation. The pump I'm installing is the Rule Mate 1100 and I'm trying to work out the best way to install the discharge hose, preferably without installing another skin fitting.

I have existing scupper drains that discharge via skin fittings at the waterline, and I'm installing on a sailing boat, so on occasion the boat can heel so that the scuppers are awash. I'm wondering whether it would be sensible / safe to insert the new bilge pump discharge into one of these hoses - does the scupper drain effectively act as the vent for a vented loop, or am I completely misunderstanding how this situation relates to vented loops?

Here is a diagram which I hope will explain it better and I've also attached a picture of the relevant page from the manual.




Any help would be very much appreciated.

Austin.

 

[Tradewinds]

IMO you'd be better with a Y rather than a T

I found that water from the bilge pump spat upwards and out when pumping out with a T.

The illustration also shows a bit of a swan-neck which would be made easier by fitting a Y piece.

 

[earlybird]

Agree about the "Y". Also, if the scupper was temporarily flooded, water might backflow through a centrifugal pump, this could be avoided with a simple non-return valve.

 

[coopec]

avoided with a simple non-return valve.

I have a similar problem. The lowest part of the bilge is the compartment immediately in front of the center cockpit. I'm thinking of installing th bilge pump in that compartment and then bring a hose up behind the steps and discharge into the cockpit. Of course if the yacht gets pooped I need some sort of non-return valve. I do have a rubber flap that normally fits over a transom exhaust that may do the job?

 

[earlybird]

Whale do an in-line NRV for ~£12

 

[VicS]

Agree about the "Y". Also, if the scupper was temporarily flooded, water might backflow through a centrifugal pump, this could be avoided with a simple non-return valve.

I have a similar problem. The lowest part of the bilge is the compartment immediately in front of the center cockpit. I'm thinking of installing th bilge pump in that compartment and then bring a hose up behind the steps an discharge into the cockpit. Of course if the yacht gets pooped I need some sort of non-return valve. I do have a rubber flap that normally fits over a transom exhaust that may do the job?

Whale do an in-line NRV for ~£12

The installation instructions for the Rule Mate pumps indicate that a non return valve should not be fitted http://www.seasea.se/UserFiles/Bygg...ocuments/ArticleDocuments/Manual RuleMate.pdf ( Page 14)

 

[rogerthebodger]

I use a fitting like this

With a fitting like this screwed onto it so as to make a tee with 2 legs in the same direction

Or this

And one of these make a great U bent for the top of the swan neck

 

[earlybird]

These centrifugal pumps don't develop much pressure head, so a NRV will reduce the flowrate somewhat, perhaps suck-it-and see!
Sharing an existing skin-fitting does impose some potential problems. Depends what the OP wants I suppose.

 

[rogerthebodger]

When you say " occasion the boat can heel so that the scuppers are awash " do you mean the skin fitting just above water level or at deck level.

If its at deck level water will flood down the pump discharge pipe. As has been said a NRV may prevent that but I would not rely on that unless you can fit a loop in the pump discharge pipe way above the heeled water level,

If the skin fitting goes below water level if you are pumping and the pump stops that could cause a back flow due to siphon effect. I did have that happen once.

 

[PlankWalker]

When the pump finishes pumping, water that is left in the pipe runs back down the pipe through the pump into the bilge.

If the outlet is below sea-level the siphon created will sink your boat in minuites if you dont have an efective float switch, anti-siphon device or non return valve.

Plank

 

[aussi]

IMO you'd be better with a Y rather than a T

I use a fitting like this

Interesting, I hadn't thought about the flow into the pipe and potential 'updraft'. I'll have a think about a 'Y' or similar, thank you for the examples.

I initially discounted the NRV because as VicS says, the manual explicitly says don't fit one (assuming this is because of the flow rate issue that earlybird points out).

When you say " occasion the boat can heel so that the scuppers are awash " do you mean the skin fitting just above water level or at deck level.

If its at deck level water will flood down the pump discharge pipe. As has been said a NRV may prevent that but I would not rely on that unless you can fit a loop in the pump discharge pipe way above the heeled water level,

If the skin fitting goes below water level if you are pumping and the pump stops that could cause a back flow due to siphon effect. I did have that happen once.

Now that's what I was worried about. Yes I mean the water level reaches the top of the diagram when heeled. Thank you Roger, you've confirmed my fears, I think I'll have to reconsider this and route the discharge all the way out to the stern for safety.

If the outlet is below sea-level the siphon created will sink your boat in minuites if you dont have an efective float switch, anti-siphon device or non return valve.

Yes, but it wasn't clear to me whether the scupper drain would act as an anti-siphon device in my planned arrangement.

 

[pvb]

I think I'll have to reconsider this and route the discharge all the way out to the stern for safety.

That would be the sensible option.