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Automatic bilge pump - non return valve advisable or redundant?


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Hi

So at present I have a bilge pump without a float switch fitted and I very rarely need to use it, but as I expect to be away for long periods in the near future I'm going to fit a pump with an integral float switch. Something like the Amarine Made 12v 1100gph which has good reviews on amazon. Several pumps of different brands seem to be exact copies of each other, so if you have a recommendation of a more reliable one let me know.
 

Yes, 1100gph for a couple of drips when it rains is a bit ridiculous but the difference in price to a 600gph is not worth the saving, and I may decide to use it for something else in the future where more force may be needed.
 

My question is if it's advisable to fit a non-return valve on the waste water hose, close to the pump, in order to avoid all the water in the hose from flowing back?

So as the exit point of the waste pipe will be about 1M higher and about 1.5M in length there will be some water in it at the moment the bilge water level on the bilge drops enough to for the pump to switch off.

Or do these pumps usually have a non return valve already fitted internally?

Thanks

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11 minutes ago, pedroinlondon said:

Hi

So at present I have a bilge pump without a float switch fitted and I very rarely need to use it, but as I expect to be away for long periods in the near future I'm going to fit a pump with an integral float switch. Something like the Amarine Made 12v 1100gph which has good reviews on amazon. Several pumps of different brands seem to be exact copies of each other, so if you have a recommendation of a more reliable one let me know.
 

Yes, 1100gph for a couple of drips when it rains is a bit ridiculous but the difference in price to a 600gph is not worth the saving, and I may decide to use it for something else in the future where more force may be needed.
 

My question is if it's advisable to fit a non-return valve on the waste water hose, close to the pump, in order to avoid all the water in the hose from flowing back?

So as the exit point of the waste pipe will be about 1M higher and about 1.5M in length there will be some water in it at the moment the bilge water level on the bilge drops enough to for the pump to switch off.

Or do these pumps usually have a non return valve already fitted internally?

Thanks

Are you sure that is an automatic pump?  image.png.c911a2b7385bd09fd39494bda0067235.png

Edited by ditchcrawler
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5 minutes ago, ditchcrawler said:

Are you sure that is an automatic pump?  image.png.c911a2b7385bd09fd39494bda0067235.png

 

That would appear to be 'automatic' when a float switch is included.

 

Running the 'float switch' wire thru an On/Off switch would make it manual, whilst running both wires directly to the battery would make it permanently 'On'

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To answer the question, you don’t need a non return valve, it’s  just something to block and cause trouble.  Most (all?) bilge pumps don’t pump out everything, mine leaves about an inch of water.  The official reason is that any oil or grease in the bilge will float on the surface and not be pumped out into the canal, you just pump out the water below, but actually it’s because it is expensive to make a float switch that is sensitive enough to pump it dry without leaving the pump running forever.

3 minutes ago, pedroinlondon said:

That is indeed an automatic pump

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The problem with automatic float switches is that sooner or later they all don't, or they stick in the up position before that.

 

The first fault means the pump is useless.  The second fault means the pump runs till it burns out or until the battery is flat (and knackered).

 

Better to ask a reliable mate, or your marina, to keep an eye on it and pump if and when needed.  Filling with water is not the only problem that can arise  when your boat is left for some time so they can look out for other problems too.

 

A non return valve is not needed either.  If will slow the flow, get clogged with something or fail to open.

 

N

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10 minutes ago, Chewbacka said:

To answer the question, you don’t need a non return valve, it’s  just something to block and cause trouble.  Most (all?) bilge pumps don’t pump out everything, mine leaves about an inch of water.  The official reason is that any oil or grease in the bilge will float on the surface and not be pumped out into the canal, you just pump out the water below, but actually it’s because it is expensive to make a float switch that is sensitive enough to pump it dry without leaving the pump running forever.

That is indeed an automatic pump

Thanks. I think this one (or perhaps another one I looked at) switches on at 2 inches of water and off at 1 inch.

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15 minutes ago, Chewbacka said:

To answer the question, you don’t need a non return valve, it’s  just something to block and cause trouble.  

The only situation where it might possibly be of use would be if the outlet for the bilge pump were very close to the normal waterline of the boat, in which case, it would stop the boat sinking from water flowing in via the outlet, right up until the valve sticks open. The better solution is obviously to block/weld up this hole and put the bilge pump outlet sensibly high up. Certainly the case with narrowboaty type boats.

Jen

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5 minutes ago, BEngo said:

The problem with automatic float switches is that sooner or later they all don't, or they stick in the up position before that.

 

The first fault means the pump is useless.  The second fault means the pump runs till it burns out or until the battery is flat (and knackered).

 

Better to ask a reliable mate, or your marina, to keep an eye on it and pump if and when needed.  Filling with water is not the only problem that can arise  when your boat is left for some time so they can look out for other problems too.

 

A non return valve is not needed either.  If will slow the flow, get clogged with something or fail to open.

 

N

Well I'm not in a marina and the buffalo boards are fairly heavy to lift (widebeam) and I don't always have mates with boats moored nearby.

I would also fit an inline fuse so that's one more thing that could go wrong on top of the pump malfunctioning as you very well said.
The starter battery was quite cheap :) so worst case scenario would be abnormally heavy rain fall and the pump not waking up.

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1 minute ago, pedroinlondon said:

 

The starter battery was quite cheap :) so worst case scenario would be abnormally heavy rain fall and the pump not waking up.

 

If you run an automatic bilge pump from the starter battery you may come back to the boat to find the battery too flat to start the engine, so then you can't recharge the battery!

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2 minutes ago, David Mack said:

 

If you run an automatic bilge pump from the starter battery you may come back to the boat to find the battery too flat to start the engine, so then you can't recharge the battery!

The starter battery is connected to a dedicated  40W solar panel so it should be ok. I don't expect the pump to run a lot quite frankly.

 

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2 minutes ago, David Mack said:

If you run an automatic bilge pump from the starter battery you may come back to the boat to find the battery too flat to start the engine, so then you can't recharge the battery!

This^^^^. The domestic bank will also be much larger and less likely to be flattened by a long run of the pump.

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6 minutes ago, Jen-in-Wellies said:

The only situation where it might possibly be of use would be if the outlet for the bilge pump were very close to the normal waterline of the boat, in which case, it would stop the boat sinking from water flowing in via the outlet, right up until the valve sticks open. The better solution is obviously to block/weld up this hole and put the bilge pump outlet sensibly high up. Certainly the case with narrowboaty type boats.

Jen

I see, thanks. It's quite far from the bilge so no.

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1 hour ago, Chewbacka said:

To answer the question, you don’t need a non return valve, it’s  just something to block and cause trouble.

I think on a canal boat there is no need of a non return valve. It is more often used on sea going vessels so as any water/waves will not run down the bilge pump outlet and fill the boat with water.

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5 minutes ago, ditchcrawler said:

The information for that one is here http://www.seaflo.com/en-us/product/detail/632.html complete with drawings

It is worth pointing out that as it is a high capacity pump it has a 1 1/8inch (approx 28mm) outlet, there is a good chance your existing pump uses a 3/4” pipe.  In which case............

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And bear in mind that in thirty years of boating I have always bought good quality automatic bilge pumps, and on every occasion when they should have worked, they haven't. Result, one sinking, two near sinkings. I still have one, but I wouldn't trust it and am surprised so many do.

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2 minutes ago, Arthur Marshall said:

And bear in mind that in thirty years of boating I have always bought good quality automatic bilge pumps, and on every occasion when they should have worked, they haven't. Result, one sinking, two near sinkings. I still have one, but I wouldn't trust it and am surprised so many do.

I know what you mean. On a 36 ft sea going boat I have 6 automatic bilge pumps and a bilge pump monitor. A lot of people say it is way over the top, but makes me feel happy.

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14 minutes ago, Arthur Marshall said:

And bear in mind that in thirty years of boating I have always bought good quality automatic bilge pumps, and on every occasion when they should have worked, they haven't. Result, one sinking, two near sinkings. I still have one, but I wouldn't trust it and am surprised so many do.

On Fulbourne we have a gizmo which sends text messages when the automatic bilge pump cuts in and out, and also sends daily text messages to say it is still working. And the system still failed and left us with more bilge water in the boat than it should have done...

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I was very glad when the float switch on ours failed last year. We had a diesel leak while I was away from the boat, and the combination of diesel plus stern-tube grease formed a sort of glue that kept the float stuck down - so we didn't pump 100 litres of diesel out into the marina.

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That is the problem with automatic bilge pumps, that and when the float jams they rather tend to flatten the batteries. In over 20 years of owning a cruiser stern with not very efficient deck drains the accumulated water never went above the engine beds. That is with being away from the boat for six weeks to two months at a time plus at one time a weep from a faulty weld.

 

On most wooden boats I an sure automatic bilge pumps are vital but of half decently maintained metal or GRP hulls I rather doubt they are.

Edited by Tony Brooks
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2 minutes ago, Tony Brooks said:

That is the problem with automatic bilge pumps, that and when the float jams they rather tend to flatten the batteries. In over 20 years of owning a cruiser stern with not very efficient deck drains the accumulated water never went above the engine beds. That is with being away from the boat for six weeks to two months at a time plus at one time a weep from a faulty weld.

That is a problem with this type of pump and it is a good idea to clean them out occasionally if at all possible. On the other hand how do people feel with the newer types of automatic pumps that do not have a float but rely on water sensing.

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1 minute ago, Steve56 said:

That is a problem with this type of pump and it is a good idea to clean them out occasionally if at all possible. On the other hand how do people feel with the newer types of automatic pumps that do not have a float but rely on water sensing.

Some run the motor ever x minutes and monitor the current so keeps it running until   the load from pumping water and thus the current falls. Others use some form of sensor to  detect water around probes. The first will eventually flatten the batteries while I would not trust the second type not to be affected by oil and grease in the water. Anyone got long term practical experience of these pumps?

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Just now, Tony Brooks said:

Some run the motor ever x minutes and monitor the current so keeps it running until   the load from pumping water and thus the current falls. Others use some form of sensor to  detect water around probes. The first will eventually flatten the batteries while I would not trust the second type not to be affected by oil and grease in the water. Anyone got long term practical experience of these pumps?

Thats the way I feel about them. I do remember a couple of years ago I installed a pump of the first one you mentioned for a customer. A week later the customer was complaining that something was making a noise and keeping her awake. It turned out to be the pump.

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