ADDING AN ELECTRIC BILGE PUMP -HOW TO PLUMB?

alisdair4

alisdair4

Well-Known Member
Joined
18 Jan 2004
Messages
690
Location
Isle of Bute
midnightdrifter.net
My Rival has a fairly deep bilge, and two manual bilge pumps, one operated from on-deck, and one from the cabin sole. I want to add an automatic pump, as the boat is going to live on a mooring. I want to use the existing pump outlet(s) , so must tee in to the outlet above the manual pump. The question is: does the non-return valve go in the outlet pipe from the manual pump (about 40mm ID) or the electric pump (19mm ID) ie, if there is no NRV in the larger pipe, could water that is pumped up electically drain back in via the manual pump. Sorry this sounds complicated -I would attach a diagram but I don't know how to!
 
Theoretically, you'd need non-return valves in both. I don't like non-return valves in bilge pump pipes - prefer a separate outlet for the electric one.
 
Definitely recommend a dedicated outlet pipe, I've tried teeing/y'ing, using other outlets and it rarely works due to pressure differences etc. You need to consider worse case scenario, because if something can go wrong on a boat - it will!
 
Why not let the electric pump push water through the manual one - fit it to the end of the suction feed. No T's no non-returns - simple. That's what is fitted in a friends fishing boat when I re-wired his pump.
 
[ QUOTE ]
Why not let the electric pump push water through the manual one - fit it to the end of the suction feed. No T's no non-returns - simple. That's what is fitted in a friends fishing boat when I re-wired his pump.

[/ QUOTE ]Surely the much smaller diameter of the electric pump's piping would seriously reduce the efficiency of the manual pump?
 
The answer to the question is 'the electric pump'. Your manual pump effectively has two non-return valves already, the pump's own suction and discharge valves. You would then be relying on the NRV to prevent manually pumped water from entering the boat via the electric (centrifugal) pump. As said by others, NRVs should not be relied on, although if yours is above the water line there is only a minor chance of a problem.

A theoretical alternative that does away with NRVs is to plumb the electric pump through the manual one, and some installations do this. However, in most cases the friction is so great that the electric pump fails to deliver sufficient flow at the increased system pressure.
 
I Y'd into my sink outlet .... so I leave that open when boat is left.

The discharge pipe from the bilge pump comes up under the sink .. loops up right up tight under the worktop and then down again to the overboard ... no need for any NR valves at all. The height of pump pipe under the worktop stops any backflow from sink and I never have bilge water in the sink.

I had absolute requirement to NOT cut another hole in the hull ... I also do not trust NR valves in any form.
 
Read the post...

[ QUOTE ]
I don't know - he doesn't say what size the feed pipe is?

[/ QUOTE ]His original post said it's 19mm.
 
Re: Read the post...

Nope, he says the outlet from the manual pump is 40mm and the electric pump is 19mm. With hindsight, I suspect the feed to the manual pump is also 40mm, but he doesn't say.

However, I'm not convinced the reduced bore will significantly affect the flow rate the manual pump can achieve.
 
Re: Read the post...

Yes, I hear what you are saying - I'm sure this would be true if the main pump was electric. 40mm bore tube/pump can shift a lot of water, approx. 4x as much as 19mm, this is logical, but when the pump is hand-powered I'm not so sure you would notice in practise.

Just my opinion, of course.
 
Hi
We've just installed a third pump on our boat. We have a huge manual thing (the diaphragm is around a foot across!) and a diaphragm electric one.
The one we put in is the Rule Gold 3700 as that will shift a serious amount of water (best rating is a gallon a second!). We used inch and a quarter internal diameter pipe and fittings. We bought a proper one way valve from Sea Screw here (and all the other fittings and pipe as they do excellent kit at a fraction of the prices in the local chandlery)
The instructions that came with the pump state you should have an exit above the water line so we did just that with a dedicated run and outlet.
If you have the ability to do so, why would you potentially compromise your ability to get rid of water in an emergency by sending it through some weird shared arrangement.
Also, do not route your new pump electric supply via the domestic fuse board, take the power straight from the battery side as you don't want the boat to sink because someone switched off the panel. For the same reason, increase the inline fuse on the system so a low ampage fuse doesn't blow and cause the same issue.
D
 
Another way of doing this would be to fit a manual change over valve which gets rid of the need for non return valves.
Fitted in the outlet line so it could be selected to manual when you are on board and to auto just before you leave.
 
--- Also, do not route your new pump electric supply via the domestic fuse board, take the power straight from the battery side as you don't want the boat to sink because someone switched off the panel. For the same reason, increase the inline fuse on the system so a low ampage fuse doesn't blow and cause the same issue. ---

I'm always very wary about this sort of advice. Personally, if I switch off my electrical system I want it to be OFF. Some people leave bilge pumps, VHF, some lights, etc directly connected to their batteries but this is not a practice that I would advocate. Why should someone swith the main breaker off? Mine generally stays on from May to October, which is when we occupy the boat.

Fuses should be rated to protect the wiring, not the appliance. Making arbitrary decisions to increase fuse sizes could lead to all sorts of problems.
 
Quite - that's why I had to replace my friend's bilge pump in the first place.

He had originally wired it direct to the battery (at least it went through a switch first), and the pump had jammed on a pebble or a bit of fishing line. The stall current was enough to burn out the wiring - causing a potentially nasty fire on board, while at sea!

The pump (Rule 500) states it should have a 2.5A fuse (if I recall). The upshot was, I re-wired the whole boat for him, including a proper fuse/switch panel. The master switch isolates everything (except the Yanmar control panel, which goes direct to the battery - I hope it includes it's own fuse!).
 
Simple question - why do you bother to have an automatic bilge pump fitted?
If you want protection when you are away (or on board and haven't noticed a sudden ingress of water) then what is the problem with wiring it direct?
If you switch off the main panel and your automatic bilge pump is no longer active, then I find that bizzare behaviour.
 
If you fit the right sort of switch, it shouldn't stay on as it will not allow debris under the swictch itself.
If you use heavier duty wire that you feel you should, you should be OK as far as higher current is concerned.
I want my pump to work if there is too much water in the bilge full stop.
I don't want it to fail and have a sunken boat because of too low a fuse rating or the fact that someone switched off the panel etc.
 
I don't have and have never had an automatic bilge pump. I close all my seacocks when I leave the boat. If I had one for a good reason, e.g. a wooden boat that always allows some leakage, I would consider having a dedicated battery for it.
 
[ QUOTE ]
I don't have and have never had an automatic bilge pump. I close all my seacocks when I leave the boat. If I had one for a good reason, e.g. a wooden boat that always allows some leakage, I would consider having a dedicated battery for it.

[/ QUOTE ]

Ummmm and that brings in questions ... direct wired ? How large a battery is necessary between your visits to sustain the pump functions ...

My boat collects condensation into the main bilge under main cabin sole .. like most GRP boats of single skin - it has this trait. So my auto-pump was there to make sure it didn't collect too much ... I used to leave my boat in UK for months on end between my rare visits .. sometimes only once per year.

After 6 years of that pump being fitted ... I hae never had cause to question it's installation. It is direct wired with own fuse inline. It has a boxed float switch that cannot get debris / other in to lock it on ... it discharges via the sink overboard.

It works fine.
 
You must log in or register to reply here.

Other threads that may be of interest

S
Can’t find a simple decent moveable pump to shift water
2
Replies
24
Views
700
Misterbreeze
M

Share this page

Top