Shower pump as auxiliary bilge pump?

[Tim Good]

I was replacing my Whale Gulper shower pumps last night (x 2) which feed into the grey tank. Both are located under the floor boards and not far from the bilges. I thought, why not put a diverted valve just near the intake for the pump and feed a line down into the bilges.

Then in the case of a drastic emergency, I could very quickly convert two shower pumpers into bilge pumps.

A very easy modification. Anyone see any reason why not?

View attachment 45857

 

[Phoenix of Hamble]

I've done exactly that.... adds a decent amount of extra capacity to the system. Mine doesn't go to a grey tank as I don't yet have one, so you might want to think about oil products ending up in there though.

 

[ffiill]

You might find a problem anywhere where the use of grey water tanks is obligatory!
Cross contamination and the like however unlikely or even impossible.

 

[pmagowan]

I was doing some research into bilge pumps and the standard pumps have no chance of keeping up with even a small breach in the hull such as a through-hull failure. In reality a bilge pump is there to help pump the water out once a leak has been sealed. The only exception is engine driven high volume pumps. So, if you spring a leak, in most cases the primary objective should be to identify its source and stop it. Spending time switching valves to activate these pumps is just more sinking time. The best thing is to have an alarm so that you are aware of a leak before the cabin sole is flooded. Then you should have a plan for checking all likely leak points, heads, through-hulls, rudder stock, prop shaft etc. Once the leak is stopped you have plenty of time to pump out and, if you wish, you could activate your shower pumps.

 

[prv]

Shower sump pump divertable to bilge pump is perfectly sensible - I have exactly that, except that mine has a wandering hose to suck up water from places that don't drain to the main strum box (shallow-bottomed modern boat with internal frames). But if you have a grey-water tank then I'm a bit puzzled - what's the point of pumping bilge water into that tank? I guess you have a second pump that empties the tank overboard? In which case that's going to be the limiting factor in the system, and you might as well plumb that one to the bilge instead of the shower pumps.

Pete

 

[sailorman]

I was replacing my Whale Gulper shower pumps last night (x 2) which feed into the grey tank. Both are located under the floor boards and not far from the bilges. I thought, why not put a diverted valve just near the intake for the pump and feed a line down into the bilges.

Then in the case of a drastic emergency, I could very quickly convert two shower pumpers into bilge pumps.

A very easy modification. Anyone see any reason why not?

View attachment 45857

Thats how the old race boats got over the 2 x bilge pump rule

 

[Phoenix of Hamble]

I was doing some research into bilge pumps and the standard pumps have no chance of keeping up with even a small breach in the hull such as a through-hull failure. In reality a bilge pump is there to help pump the water out once a leak has been sealed. The only exception is engine driven high volume pumps. So, if you spring a leak, in most cases the primary objective should be to identify its source and stop it. Spending time switching valves to activate these pumps is just more sinking time. The best thing is to have an alarm so that you are aware of a leak before the cabin sole is flooded. Then you should have a plan for checking all likely leak points, heads, through-hulls, rudder stock, prop shaft etc. Once the leak is stopped you have plenty of time to pump out and, if you wish, you could activate your shower pumps.

But there is a decent chance that you can slow the ingress from a hull breach, but not stop it... in which case you'll be grateful for every single millilitre that you can pump overboard automatically!

 

[Tim Good]

whats the point of pumping bilge water into that tank? I guess you have a second pump that empties the tank overboard? In which case that's going to be the limiting factor in the system, and you might as well plumb that one to the bilge instead of the shower pumps.
Pete

Well you're dead right there. Basically the two shower pumps are half the capacity of the main grey tank pump so I may as well rig one valve onto the main grey pump rather than onto the shower pumps.

I like your idea of a wandering line though. That said for a line to be flexible enough to roam around the cabin it would have to be just a normal water hose and that probably could not cope with the capacity the pump is trying to kick out?

Thoughts?

 

[prv]

But there is a decent chance that you can slow the ingress from a hull breach, but not stop it... in which case you'll be grateful for every single millilitre that you can pump overboard automatically!

It's true that every bucketful chucked out by an automatic pump is helpful, but he's right that the flow rate of most yacht pumps (and a shower sump pump is going to be at the bottom of that scale) is fairly insignificant against a seacock-sized hole. If the pump started emptying the bilge automatically then fine, but a shower pump is generally manually switched and it needs the intake valve changing over, so it's not automatic. The time taken to put it into action is probably better spent finding and stopping the leak.

Hopefully there will be a larger centrifugal main bilge pump kicking into action with a float switch.

Pete

 

[Tim Good]

But there is a decent chance that you can slow the ingress from a hull breach, but not stop it... in which case you'll be grateful for every single millilitre that you can pump overboard automatically!

Yeah I would agree. It takes 30 seconds to switch a valve and turn on another pump. If it took you 15 mins to locate the leak, an hour to stem the main flow and another hour to stop the flow altogether then that's nearly another 2 tonnes of water out of the boat by the time all is said and done.

That's assuming 15L per minute which a reasonable grey tank pump like mine would do.

 

[CFarr]

A surveyor recommended to me that a diverter fitted to the raw water in pipe was a powerful bilge pump. In extremis only you understand and when you can't keep up with manual pumping, which you can't for extended periods.
Not sure about bilge water going into the engine but if sinking I'd assume you'd be glad of it, as long as the engine is working of course.

 

[prv]

I like your idea of a wandering line though. That said for a line to be flexible enough to roam around the cabin it would have to be just a normal water hose and that probably could not cope with the capacity the pump is trying to kick out?

It's just some transparent unreinforced PVC hose - the transparent nature is useful to check that water is indeed moving up it as my pump occasionally fails to prime.

Not sure I understand your point about capacity - are you suggesting that the pump has such a high flow rate that a 1/2" hose won't let enough water in? In that case, what on earth kind of shower do you have on board and how big are your water tanks?

Pete

 

[pmagowan]

But there is a decent chance that you can slow the ingress from a hull breach, but not stop it... in which case you'll be grateful for every single millilitre that you can pump overboard automatically!

Not really. The difference in capacity of the pumps compared to the rate of inflow of water means that the time spent trying to activate them is unlikely to be worth it. In a flooding situation the first few minutes are the most important as you still have clues as to where the water is coming from. If you spend them activating pumps then you will just find a steadily rising lake of water in the bilge without any signs of the direction of flow. Remember that the capacity of a pump is rarely what it actually pumps as it doesn't take restrictions like valves and head of water to overcome into account. I think, in general, pumps should be used for v small leaks, such as the odd bit of rain or stern gland drip, or they should be used to pump out water after a leak is sealed. They should not be considered a significant force for keeping up with a leak or buying time unless they are high volume engine driven pumps. Worrying about the pumps is only likely to distract from the job of identifying and sealing the leak.

 

[prv]

Yeah I would agree. It takes 30 seconds to switch a valve and turn on another pump. If it took you 15 mins to locate the leak

Fifteen minutes?!? If it was a sheared-off seacock I think you'd have long since sunk by then! I'd hope to have found a hole and got something over it, even if just my foot, within thirty seconds of starting to look (the time between the hole appearing and us realising and starting the search is a different question, as I know from experience). Hence why an additional thirty seconds to turn on a very small pump doesn't make much sense.

Pete

 

[pmagowan]

Yeah I would agree. It takes 30 seconds to switch a valve and turn on another pump. If it took you 15 mins to locate the leak, an hour to stem the main flow and another hour to stop the flow altogether then that's nearly another 2 tonnes of water out of the boat by the time all is said and done.

That's assuming 15L per minute which a reasonable grey tank pump like mine would do.

15l/min against about 250l/min of a through hull failure!

you don't have 2 hours 15 minutes to play around with!

It should be 60 seconds to find the leak, 20 seconds to stop it!

 

[prv]

A surveyor recommended to me that a diverter fitted to the raw water in pipe was a powerful bilge pump.

Presumably you have a quick look at the water coming out of the exhaust when you start the engine, to check it's flowing.

Would you call that flow "powerful"?

On any sailing yacht I've been on, I wouldn't.

Pete

 

[Tim Good]

15l/min against about 250l/min of a through hull failure!

you don't have 2 hours 15 minutes to play around with!

It should be 60 seconds to find the leak, 20 seconds to stop it!

I think in the case of that sort of breach I totally agree with you. Don't mess about with anything other that sticking everything, including the cat, into the hole.

 

[chinita]

The engine powered secondary pump is the system which is recommended by Steve Dashew, the American cruising guru.

I applied it to a previous boat. One simple valve, a length of hose into the sump bilge and the 152hp Thorneycroft took the strain.

Never had to use in in anger, thankfully.

 

[pmagowan]

I think in the case of that sort of breach I totally agree with you. Don't mess about with anything other that sticking everything, including the cat, into the hole.

That is, by far, the most common breach. Through-hulls fail. At that rate an average boat is well sunk in 30 minutes. The additional pump, in best circumstances, gives you an extra 110 seconds. In reality it probably achieves half it's rated capacity and will fail when the electrics are flooded so you might get an extra 30 seconds before abandoning the boat.

 

[Tim Good]

The engine powered secondary pump is the system which is recommended by Steve Dashew, the American cruising guru.

I applied it to a previous boat. One simple valve, a length of hose into the sump bilge and the 152hp Thorneycroft took the strain.

Never had to use in in anger, thankfully.

Excuse my ignorance but once the engine air intake is submerged then its game over for that plan. On my boat it wouldn't take too long for that to happen. The batteries are much higher thankfully. Maybe different on others.