Bilge pump installation

[PaulJ]

I have been conducting some experiments prior to installing a bilge pump in my 39ft long-keeled boat.

Plan A had been to install the pump just under the floor boards in the cabin and the discharge skin fitting as high as possible under the gunwale. This would mean that the pump had to suck the water though a height of about 3ft and then pump it a further 6ft.

My experiment with a bucket of water and fixing the 1 1/2 inch pipe about 9ft up showed that this configuration is simply not practical because it is extremely hard work pumping the water through that height and the rate of flow is just not adequate.

So Plan B was developed which involved taking the discharge hose up to the same height but then bringing it down again about 3 ft in the hope that the syphon effect of the piece of pipe coming down would reduce the pumping effort required. Alas this had no effect because the water ran out of the pipe faster than I could feed it with the pump so air went up the pipe and there was no syphon effect.

The only other solution I can think of is to have the discharge skin fitting just a little above the waterline so that the water doesn't have to be lifted so far and a seacock in the discharge pipe to prevent an ingress of water when the boat heels. I am not keen on the idea of putting a seacock in the discharge pipe because it is one more thing to do in a panic situation and there is always the danger of forgetting to open it. There is a non return valve in the pump but these valves always allow a small amount to flow back over time and anyway I wouldn't want to rely on that alone.

My questions are these... Firstly, to the surveyors out there, is there any regulation that says you can't have a seacock in a pump discharge pipe? Secondly, has anybody got any better ideas?

Oh, and before anybody points out that I have to have a pump which can be operated from the cockpit...... I do have one but it discharges through the transom so there is not the same problem.

I would welcome your thoughts......

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[Becky]

I found myself in a somewhat similar situation, in that the boat I bought this Spring had an electric bilge pump beneath the engine, with a horizontal pipe to an exit just above the water line. Admittedly there was a non-return valve in the pipe run, but there was little risk of water coming in, as she never left her mooring during the period of ownership of the previous person. On the other hand, I had copious quantities of water making its way into the bilges, and causing considerable worry, until I found the problem ( dirt in the non-return valve). My solution was to re-run the pipe with a large loop up under the side deck, with an extra joker non-return valve. For me, this has been successful, in that I can still empty the under-engine sump, (and I am sure the syphon effect helps) while preventing ingress of the Solent. I think this was a better solution than to cut another hole in the topsides to discharge water at a sensible height above the water line.

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[charles_reed]

Why not route it out through the transom?

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[roger]

I suspect you just dont have a powerful enough pump.
In any case a long suction leg is bad news. Most cheap pumps have the pump below water level and they work reasonably well. The lower you can get it usually the easier it will prime.

<hr width=100% size=1>Roger

 

[Dave_Knowles]

Bilge pumps due there design do not pump at a very high pressure. I tried about six when I fitted a filter and it was a disaster. If you change the outlet size also problems seemed to arise once again due to their design. The answer in my case was to fit a Jabsco Pup pump which is self priming. This cost a little more but it has lots of pressure and really works a treat. Another good thing is the pump is fitted on the bulkhead well out of the way of the water and I can easily reack it if I need to do anything to it. I have fitted a strum box in the bilge with a valve to stop backflow.

<hr width=100% size=1>Take care.

Dave

Dave Knowles
Southampton - UK

http://www.MyCleopatra.co.uk

 

[Strathglass]

You need to get the pump as low as possible, right down in the water, Have a high loop above the waterline even when heeled, non return valve and outlet above the static waterline.

Try your bucket experiment with as short an inlet pipe you can get.

Iain

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[Maurice55]

If you want to have your pump in the cockpit, the problem is the pump ability to suck up the about 2.5m?? from your bilges. Is it not a question of type of pump, I gess a membrane pump is not very good at that but it is not unreasonably high, I used to pump water out of a well much deeper than that but the pump was a double action bronze type of thing, very efficient as I remember.
Is this of any help?
Maurice.

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[Guest]

If you have self-draining cockpit .... then discharge to cockpit

To do the original that you want ..... you will need a positive displacement pump to get the pressure and height. The average bilge-pump ... electric job is vane and this does not constitute positive pressure.

I have a 2-way valve on my sink unit, one connected to pump in bilges, other connected to sink out. There is a standard gate valve next to the hull ...... as I don't like non-returns ..... When my boat heels to starboard, I do have the outlet below water and it does back-flow ..... reason for proper valve on the fiiting. I do plan to change this to another fitting which will discharge to transom outlet ..........

You can have the shortest inlet pipe, good speed on the pump - but if it has to push the water up so high ......... positive displacement is only way.


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I came - cos they said was FREE Guinness !
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[PaulJ]

Thank you one and all for your responses, where comment is required I will attempt to take them in order....

Becky, as I said in my initial posting, I did try a loop up and then down again but it didn’t seem to help, possibly because the pipe is quite large (1 ½” i.d.) and the water was running out of the outlet at the bottom of the loop faster than I could pump to keep the pipe full at the top so air was running back up the pipe and there was no syphon effect. I guess it is possible that a non-return valve just inside the skin fitting would restrict the flow enough to prevent this from happening…. I will try it.

Charles, your suggestion of taking it out through the transom is possibly the right solution. I hadn’t considered that because the electric and other manual pump discharge there and to do it from this second manual pump would require a pipe-run of at least 23ft I have to admit that my knowledge of physics becomes a bit hazy here….. I know that ”head” is the governing factor to what a pump can do but does the sheer weight of water make a difference as well? If I were to make the outlet in the transom, say a foot above the waterline, the pump would have to “suck” the water up about 3ft and then push it up another 3ft but in a gentle incline nearly 23 ft long. With 1 ½” pipe there will be a considerable weight of water in the pipe. Would this reduce the performance of the pump more than just making a short run straight out through the side but to a similar level?

Roger, the pump is a Whale “Gusher 30” which is one of those big double acting diaphragm pumps with 1 ½” outlet. It has a handle about 2ft long and is amongst the biggest I have found. I suspect that any limitation on it’s power is going to be in the strength and fitness of it’s operator! I am thinking of the situation where we have a serious leak, which I am trying to sort out while SWMBO pumps for all she is worth.
She could be pumping for some time and I think the effort required needs to kept to a minimum.

Dave, I don’t think I have seen the Jabsco pump you mention. We are talking about a MANUAL pump are we? I do have an electric pump already, which discharges through the transom but my current dilemma concerns the manual backup.

Iain, the pick-up pipe will be a little under 3ft below the pump but this is in a kind of sump so with any significant amount of water in there the water level will be about 18” above that so the pump will only have to lift the water about another 18”…. The pump will be just below the floorboards so if the water should reach floor level then the pump WILL be under water! As I said in answer to Becky’s response, I will do the experiment again with an NRV at the outlet and see what difference it makes.

Maurice…. I’ll give you a ring!

Nigel, I am not keen on the idea of discharging into the cockpit for a number of reasons, not least because in anything other than a panic situation I wouldn’t want to squirt any poor unsuspecting soul who might be sitting there….. worse still, it might be me that gets squirted! Seriously though, with the aft cabin beneath the cockpit, it would not be possible to make a neat pipe-run. Do I remember correctly from one of your postings way back that you are a surveyor? If so, from what you say, I take it that there is no regulation that says you can’t have a seacock on a pump outlet…..? As for getting a “positive displacement” pump, I have already bought this Whale diaphragm pump so I would like to use it if possible but if I can’t reach a satisfactory solution I may have to think again.

Once again, thank you all for your responses.

Paul.


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[Avocet]

It would get very involved but perhaps you could have the pump emptying into a holding tank half or maybe 2/3rds of the way up. You could then put a cheap electric pump in the holding tank with an automatic float switch to sling the water out of the tank and over the side. Avocet has a very deep bilge (not as deep as yours though!) and we tried a good quality electric pump and float switch once. Even though the "head" was only about 6' it was a disaster because the flow rate was pretty lousy and it only worked when the battery was fully charged. We ended up in the situation where the float switch would kick-in, the pump would suck the water up out of the bilge and discharge some of it over the side. The float switch would then cut out and the water in the hose would gradually fall back down into the bilge triggering the float switch... ...and so it went on until the battery was flat! We now have good old-fashioned manual pumps! We could have sorted out the problem by tinkering with the trigger level for the float switch but we just gave up instead!

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[Avocet]

...come to think of it, you could probably have two electric pumps one feeding the other via a small tank if you wanted. Failing that, as others have said, a positive displacement pump is the only other effective solution at this height.

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[Dave_Knowles]

Hi Paul,

No the Jabsco is a self priming electic pump. Look at <A target="_blank" HREF=http://www.jabsco.com/prodInfoApp/servlet/DisplayProducts?typeId=JMBED&page=0&catalogId=Marine&categoryId=BILGE>http://www.jabsco.com/prodInfoApp/servlet/DisplayProducts?typeId=JMBED&page=0&catalogId=Marine&categoryId=BILGE</A> for the jabsco range.

<hr width=100% size=1>Take care.

Dave

Dave Knowles
Southampton - UK

http://www.MyCleopatra.co.uk

 

[Guest]

As far as I am aware ..... the only time a seacock would be advised and stated to be advisable in a report would be below waterline.

In other situations there are many that have no valve and therefore shoudl answer that one.

The outlet to cockpit was a suggestion to get around the drilling holes, long leads etc. etc. but I do agree your 'vision'. Let it be the trial that decides that via transom / cockpit works .... but also in memory I had a 'vision' of joining into the cockpit overboard to discharge the pump.

But it would seem that you are getting there eventually .....

In your original post I don't renember you clarifying it as a Whale hand pump ...... that should shift most ..... so as others basically went down the 'expected' route of electric !!!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I came - cos they said was FREE Guinness !
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[AlanPound]

"as I said in my initial posting, I did try a loop up and then down again but it didn’t seem to help, possibly because the pipe is quite large (1 ½” i.d.) and the water was running out of the outlet at the bottom of the loop faster than I could pump to keep the pipe full at the top so air was running back up the pipe and there was no syphon effect. "

... you wouldn't have this problem if your outlet was *below* the waterline...

Alan

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[PaulJ]

Hmmm.... an extra tank "half way up" would present the problem of where to put that tank and therefore I don't think that solution would be possible. However it does give me an idea.... the electric and manual pumps in the aft section of the boat operate from a higher base because there is ballast in the keel in that area so the bilge is not as deep. I still want to install the big manual pump with it's own outlet in the forward section for the "all hands to the pumps" situation, but maybe it would be a good idea to install an additional electric pump in the forward section which will shift any water to the higher aft section and thence overboard via the pumps in that section..... 'Could make it more difficult to find a leak though.....?

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[PaulJ]

You are absolutely right, I confess I never thought of that. I don't like the idea of putting a bilge pump outlet below the waterline though....... Has anybody ever seen a setup like that?

 

[AlanPound]

"I don't like the idea of putting a bilge pump outlet below the waterline though....... "

I would have thought that. with a loop high above the waterline, and an anti-siphon device at the top, and the fact it is going back into a pump, it should be ok... but I will admit that I don't *know* enough to be able to say whether this is a *smart* idea, and idea, or a *dumb* idea....

I suspect it is not actually a dumb idea... although how smart???

There are plenty of instances of below-the-waterline outlets - but I would guess the smart thing is to do what you can to minimise them... however you can't make omelettes without... etc....

Alan

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[Guest]

Be careful of siphon ....

you couild actually create a siphon ....

<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I came - cos they said was FREE Guinness !
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[TheBoatman]

Paul
The obvious answer to that is all loo outlets are below the water line. Same thing just pumping some thing different<s>

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[qsiv]

I just looked - my suction side is 9 to 12 feet long (depends which compartment I am pumping from), delivery is about 3 feet and everything runs just fine. The electric pump (an eccenric driven Henderson Mk5) has exactly the same runs and shoots the water about 5 feet out of the discharge there is so much power available.

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