Adding a second bilge pump?

[Tony1]

 

It has occurred to me- rather belatedly two years after moving aboard- that I ought to make more effort to keep the engine bay floor dry. 

My first step in achieving this laudable aim was to catch the water that drains into the engine bay from the entry-steps on the stern. So I placed a 10 litre water container and a funnel under the drain hole in the bottom step (its a Liverpool boat, and it has a wooden entry door set to one side on the stern, instead of the more normal double-opening hatch arrangement in the middle). That container has to be pulled out and emptied every 2 days or so in very rainy weather, and every week or two when its drier. 

But it occurred to me that there is room for automation in this system, so my next cunning plan is to replace the 10 litre water container with a deep plastic catchment tray that will fit into that same small area, and then to place a 12v bilge pump into that tray. 

Given how much water can sometimes drain from the steps down through that hole, it seems to make sense to catch it and suck it out automatically, in case I am ever away from the boat for a few days at time of heavy rain- or if I just forget.

So the plan is a second bilge pump specifically to remove the water that is caught underneath the stern steps-  which leads to my question. 

Would it be more sensible to cut a new drain hole in the hull on that side of the boat, or to lead the water drain tube across/around the engine bay, and create a join with the other drain tube from the main bilge pump? The main bilge pump drain hole is on the rear left 'corner' of the engine bay (looking forwards), whereas the drain for the steps is on the other side of the engine bay, and is almost level with the forward end of the engine block. 

I dont really want to cut new holes in the skin, but I'm not sure how well the drainage will work if the waste water tubing for the second pump runs from under the steps and about 2 metres diagonally across the engine bay. And as well as needing a junction for the two waste tubes, I think I might need some kind of valve to stop waste water from one tube going back down into the other tube at the junction.

 So at the moment I'm temped to cut a new hole on the right hand side where the steps are, and have a much shorter run of waste pipe to that. 

 

[David Mack]

I'd cut a new drain hole near the new bilge pump. Likely to be more effective and no chance of water being pumped by one pump going back through the other pump into the bilges.

Use a hole saw to cut a circular hole in the hull side plating and fit a skin fitting - ideally brass, but a plastic one will be cheaper. But you can paint a brass one black so it is inconspicuous against the hull.

[matty40s]

Measure up from the water line on outside to whatever height surveyors are insisting on at the moment(min 15cm?) and drill a pilot hole through if you are going to drill the main hole from in the engine bay.

[Alan de Enfield]

22 minutes ago, matty40s said:

Measure up from the water line on outside to whatever height surveyors are insisting on at the moment(min 15cm?) and drill a pilot hole through if you are going to drill the main hole from in the engine bay.

 

 

Isn't it 10 " (250mm for the foreigners)

[Tony1]

Thanks guys, I hadn't given any thought to the height above waterline.

The height of the exit hole on the left side for the existing bilge pump cant be more than 5 inches above the water, so if that's now a BSS issue then I already have something to sort out. Unless there's some kind of one-way valve on it that stops water coming back in. 

The price difference doesn't seem too bad, so brass seems like the way to go for longevity, although I will be blacking/painting over the skin fitting anyway in a couple of months. 

[Tony Brooks]

1 minute ago, Tony1 said:

Thanks guys, I hadn't given any thought to the height above waterline.

The height of the exit hole on the left side for the existing bilge pump cant be more than 5 inches above the water, so if that's now a BSS issue then I already have something to sort out. Unless there's some kind of one-way valve on it that stops water coming back in. 

The price difference doesn't seem too bad, so brass seems like the way to go for longevity, although I will be blacking/painting over the skin fitting anyway in a couple of months. 

 

Not mandatory for a PRIVATE BSS but best to play safe and stick to the 10" thing. See if you can position the skin fitting close to a rubbing band so the band protects the brass fitting.

[Tony1]

1 minute ago, Tony Brooks said:

 

Not mandatory for a PRIVATE BSS but best to play safe and stick to the 10" thing. See if you can position the skin fitting close to a rubbing band so the band protects the brass fitting.

 

Thanks Tony, I'll plan on at least 10 inches above WL. I can only imagine that the bilge pump itself, when not actually pumping, must effective seal the route for the water, and must block any water from coming back down the waste tube into the bilge. But It does seem a bit of a potential weak point at first glance, having the exit hole so close the the WL.

I'm sure I've seen turbulence in locks and even small waves in very windy weather, when the surges of water have reached a few inches above the nominal WL.

Now that its been pointed out how low it is, I'm not over the moon about it tbh, even its not mandatory for BSS.  

I wonder if I could fit another length of waste pipe in there, long enough that it has a gooseneck in it so the pipe is tilting down as it approaches the hull. 

 

 

[ditchcrawler]

28 minutes ago, Tony1 said:

Thanks guys, I hadn't given any thought to the height above waterline.

The height of the exit hole on the left side for the existing bilge pump cant be more than 5 inches above the water, so if that's now a BSS issue then I already have something to sort out. Unless there's some kind of one-way valve on it that stops water coming back in. 

The price difference doesn't seem too bad, so brass seems like the way to go for longevity, although I will be blacking/painting over the skin fitting anyway in a couple of months. 

Its not a BSS issue.  The only issue is if you require a survey for insurance, the surveyor may decide its too low

[magnetman]

I dislike excessive numbers of skin fittings. It seems wrong to cut holes in boats unless absolutely definitely certainly necessary. 

 

Can you not just pump from the collection container into the stern bilge and let the existing "main bilge pump" eject it from the boat?

 

This would depend on the design of the catchment at the stern obviously but if there is already a pump displacing water from a location in the engine bay then it seems to me to make sense to add any water coming in to that area either by gravity or a small auto pump rather than cut a hole in the boat. 

Edited January 12, 2023 by magnetman
Added a bit

[Tony Brooks]

24 minutes ago, Tony1 said:

 

Thanks Tony, I'll plan on at least 10 inches above WL. I can only imagine that the bilge pump itself, when not actually pumping, must effective seal the route for the water, and must block any water from coming back down the waste tube into the bilge. But It does seem a bit of a potential weak point at first glance, having the exit hole so close the the WL.

I'm sure I've seen turbulence in locks and even small waves in very windy weather, when the surges of water have reached a few inches above the nominal WL.

Now that its been pointed out how low it is, I'm not over the moon about it tbh, even its not mandatory for BSS.  

I wonder if I could fit another length of waste pipe in there, long enough that it has a gooseneck in it so the pipe is tilting down as it approaches the hull. 

 

 

 

It can't, those pumps are just centrifugal impellers. It will only be a pipe full of water that runs back. I would suggest you fit a swan neck at the skin fitting so rain can flow down the hull and into the skin fitting.

[Kendorr]

My new build has the stern door in the centre, but the steps go down similar to Liverpool boats.

 

I have 2 bilge pumps, as op is asking. The one under the steps is only for the tray which is under the steps and it drains through its own dedicated skin fitting.

[Momac]

4 minutes ago, ditchcrawler said:

Its not a BSS issue.  The only issue is if you require a survey for insurance, the surveyor may decide its too low

Why?

If the pipe connected to the skin fitting rises up to a higher level there is no issue 

A skin fitting could be in the bottom of the boat  and can be perfectly safe .

 

[magnetman]

There is a problem of screw-in skin fittings being broken off for example when entering a lock and rubbing a piece of metalwork on the gate. 

 

The best skin fitting is a thick wall stainless steel tube welded into the hull protruding about 8mm outboard and say 3 inches inboard to leave room for the hose.  Welded on both sides. This is the Rolls Royce solution. 

A skin fitting with a hose on it which goes upwards is simply a hole in the boat if it gets broken off. 

 

Edited January 12, 2023 by magnetman

[ditchcrawler]

15 minutes ago, MartynG said:

Why?

If the pipe connected to the skin fitting rises up to a higher level there is no issue 

A skin fitting could be in the bottom of the boat  and can be perfectly safe .

 

I have had 2 share off in the past couple of years. I wont ever have another boat built, but if I did I would have welded outlets with nothing on  the outside.

[Tony1]

30 minutes ago, Tony Brooks said:

 

It can't, those pumps are just centrifugal impellers. It will only be a pipe full of water that runs back. I would suggest you fit a swan neck at the skin fitting so rain can flow down the hull and into the skin fitting.

 

Thanks Tony, I'll put that on my jobs list.

So you can buy a swan neck as a fitting? To attach to a skin outlet/fitting? 

I need to measure the pipe size, I think it might be the 38mm type.

 

 

[magnetman]

9 minutes ago, ditchcrawler said:

I have had 2 share off in the past couple of years. I wont ever have another boat built, but if I did I would have welded outlets with nothing on  the outside.

It is okay to have a little protrusion outside. Just enough to get a weld on it. If it is close to a rubbing strake that will help to protect it.

Welded both sides will be stronger. As I said above I advocate stainless for this. It's fine to TIG stainless onto mild steel and it cuts out the problems. 

 

One of my boats has welded-in mild steel skin fittings with no protrusion and the dribbles from the outlet have compromised the weld on one of them. 

 

My other boat has the stainless double welded fittings and is ten years older and has no issues at all. 

 

 

 

 

6 minutes ago, Tony1 said:

 

Thanks Tony, I'll put that on my jobs list.

So you can buy a swan neck as a fitting? To attach to a skin outlet/fitting? 

I need to measure the pipe size, I think it might be the 38mm type.

 

 

38mm is unlikely for a normal bilge pump. That's pumpout lavatory hose size! More likely inch or 3/4 inch for a bilge pump. 

[matty40s]

36 minutes ago, MartynG said:

Why?

If the pipe connected to the skin fitting rises up to a higher level there is no issue 

A skin fitting could be in the bottom of the boat  and can be perfectly safe .

 

You might think and know that, virtually all the surveyors will advise against it.

[Tony1]

28 minutes ago, magnetman said:

There is a problem of screw-in skin fittings being broken off for example when entering a lock and rubbing a piece of metalwork on the gate. 

 

The best skin fitting is a thick wall stainless steel tube welded into the hull protruding about 8mm outboard and say 3 inches inboard to leave room for the hose.  Welded on both sides. This is the Rolls Royce solution. 

A skin fitting with a hose on it which goes upwards is simply a hole in the boat if it gets broken off. 

 

 

I totally get your point about a screw-in fitting not being 100% secure, but that said, even if it breaks off, the hole will be 10 inches above the waterline, so any water ingress will be a momentary/freak one-off splash, and I should spot the broken fitting before there is any risk of sinking. 

In an ideal world I would get the skin fitting welded on, but it will depend on finding a mobile welder, and I bet there will be  significant cost for that.

 

 

[magnetman]

Just now, Tony1 said:

 

I totally get your point about a screw-in fitting not being 100% secure, but that said, even if it breaks off, the hole will be 10 inches above the waterline, so any water ingress will be a momentary/freak one-off splash, and I should spot the broken fitting before there is any risk of sinking. 

In an ideal world I would get the skin fitting welded on, but it will depend on finding a mobile welder, and I bet there will be  significant cost for that.

 

 

I think you will be fine with a high level skin fitting in the curve of the stern. 

 

My point was about why surveyors will tend not to like them. 

 

 

 

Why can't you just route the new bilge pump to eject water into the area the main bilge pump is drawing from? 

 

Maybe the main pump is rarely used and not an automatic type. 

[Alan de Enfield]

11 minutes ago, matty40s said:

You might think and know that, virtually all the surveyors will advise against it.

 

Surveyors report :

 

The forward deck drained via openings in the hull sides, these were of adequate size and found satisfactory. The forward deck drains were a satisfactory height above the waterline (especially when considering the front door cill) however it is very easy to overload a small vessel such as this. With full water and fuel tanks and many persons and gear onboard, freeboard heights will be greatly reduced and this must be considered at all times and outlets/drains monitored regularly. If freeboard heights become much reduced then they will need revising.  
    
Essential Repairs * Ensure freeboard height of the weed hatch is at least 15cm.
    
Essential Repairs * The bilge pump outlet must be raised to above the upper full length ‘D’ bar and the current opening plated over, using 6mm plate.
    
Four skin fittings, located starboard side, were far too close to the waterline. The bilge pump outlet must be raised to above the upper full length ‘D’ bar and the current opening plated over, using 6mm plate.
    
Essential Repairs * The galley and heads sink outlet skin fittings must be fitted with isolators as these cannot be raised as they rely on gravity drainage. These isolators must be easily accessible and clearly marked and turned off on certain waters/weather conditions.
    
The galley and heads sink outlet skin fittings must be fitted with isolators as these cannot be raised as they rely on gravity drainage. These isolators must be easily accessible and clearly marked and turned off on certain waters/weather conditions.
    
Essential Repairs * The shower pump outlet must be raised to at least 25cm above the waterline and the current opening plated over, using 6mm plate.

 

Owners comments :

 

I have studied the RCD  DIRECTIVE  2013/53/EU   and also Small craft - Seacocks and through-hull fittings - Part 1: Metallic (ISO 9093-1:1994)Publication date:Feb 14, 2019 and can find no heights specified for hull outlets, only a requirement for seacocks for underwater fittings.   There is this in the BSS https://www.boatsafetyscheme.org/requirements-examinations-certification/non-private-boat-standards/part-10-non-private-boats-safety-features/hull-openings/ but only as a suggestion of 250mm height for private boats.

The lowest of these outlets is the bilge pump 0nly 9cm above the waterline with the secured hose rising well above it and the shower outlet is 13mm.

The builder says the boat conforms with the RCD and there is nothing wrong with it as it is the same as all the 200+ boats they have built, however at my request they reballasted the boat for me as it was too low in the water at the stern.     I asked the marina to get the surveyor to recheck the boat as he was due to inspect another one, I had to pay for that in advance!   The surveyor refused to alter the survey and the marina still refused to sell the boat.  

 

Thread discussing it :

 

 

[Tony Brooks]

16 minutes ago, Tony1 said:

 

Thanks Tony, I'll put that on my jobs list.

So you can buy a swan neck as a fitting? To attach to a skin outlet/fitting? 

I need to measure the pipe size, I think it might be the 38mm type.

 

 

 

That is one hell of a bilge pump for the duty described, 38mm is about 1.5", even as an OD that is a big pipe. I would expect the pump outlet to be more like 5/8" i.d.

 

I suspect tat you might have to put an elbow on the skin fitting so the swan neck is parallel with the hull side but a run of hose lead up above the skin fitting and then down to the fitting will suffice as a swan neck.

[magnetman]

One can use speedfit pipe and elbows with a bilge pump. Warmed up garden hose for flexible parts as it slips over 15mm stuff with two stainless pipe clamps at each join. 

 

A rigid bilge pump outlet pipe might be an interesting option if you want it to come down from above. 

 

 

[Momac]

20 minutes ago, matty40s said:

You might think and know that, virtually all the surveyors will advise against it.

Must be a narrowboat surveyor thing

 

[Tony1]

1 minute ago, magnetman said:

 

Why can't you just route the new bilge pump to eject water into the area the main bilge pump is drawing from? 

 

The main bilge pump is automatic, but the problem with any bilge pump is that the water has be at least few mm deep before it will kick into action, and it never removes all the water- there is always a few mm of water hanging around that it leaves behind. And ideally I'm trying to keep the bilge dry for as long as possible.

My goal is to minimise long term rust by not allowing water to collect in the bilge at all, as a general rule (and also painting with vactan etc). 

 

The main bilge pump does sit in a small vertically recessed square, about 15mm deep and maybe 30cm along each side. So in theory it should suck out any water that I tip into that little recess (from the other bilge pump), and it should suck it out before it overspills from the recess and starts running along the engine bay floor. In theory.

But yes, your idea could work, and it might be worth a try before cutting holes in the hull. So I would route the waste pipe from the second bilge pump so it drains into the small square recess where the main bilge pump is,, and let the main bilge pump suck it out.

 

It means that that the little recess for the main bilge pump will have a more or less permanent layer of a few mm of water in it, but at least the thin layer of water is contained in one small area, so any potential rust is limited to a small spot. 

 

 

 

 

[matty40s]

Just now, MartynG said:

Must be a narrowboat surveyor thing

 

No, as I explained on the other thread, it's down to the insurance companies insisting on it at the annual conference with the surveyors.