Anti Siphon Loop -- Bilge Pump

[Terra Nova]

Originally Posted by barnakiel

The vented ones are only used for below water outlets like toilets or raw water inlets on engines.

Bilge pumps normally have outlets above water plane. Hence the loop, NON vented one.

And as the trap (aka non-return) is in line just behind the pump, and hence a strainer ahead of the pump, there is hardly ever any question about having one. Otherwise the whole raise will return to the bilge every time you pump. When the raise is big diameter and long, you will flood the bilge and the pump may in some situations circulate like this forever.

People who claim non returns are stupid clearly never seen diaphragm bilge pumps on ships? Open one, look inside, there will be two non returns in the design, at times more. Very stupid design used commonly on maxi yachts.

Not sure why solutions that are common place on serious boats are a matter of so much discussion here.

b.

Lots of misinformation here.

[barnakiel]

Originally Posted by Terra Nova

Lots of misinformation here.

Maybe later you will have more time to expand on this, and set the record true?

Which of my opinions do you find mis-informing? Everything?

I am not one of those who get offended when faced with hard facts against opinions. Ready to turn around and admit mistakes, when such found.

Imagine someone stumbles upon and now they know you are right I am wrong. Without you more detailed info on which opinions differ and how, there is little use for those who may be reading the thread in a year or two.

Unless you mean I post misinformation on purpose. But I know you do not.

Cheers,
b.

[cal40john]

Originally Posted by barnakiel

The vented ones are only used for below water outlets like toilets or raw water inlets on engines.

Bilge pumps normally have outlets above water plane. Hence the loop, NON vented one.

And as the trap (aka non-return) is in line just behind the pump, and hence a strainer ahead of the pump, there is hardly ever any question about having one. Otherwise the whole raise will return to the bilge every time you pump. When the raise is big diameter and long, you will flood the bilge and the pump may in some situations circulate like this forever.

People who claim non returns are stupid clearly never seen diaphragm bilge pumps on ships? Open one, look inside, there will be two non returns in the design, at times more. Very stupid design used commonly on maxi yachts.

If you happen to not own a maxi yacht, just open your toilet pump and look inside. Once is enough. Can you NOT see the non return valves? And yet thick brown matter will pass and not clog it. How odd.

Not sure why solutions that are common place on serious boats are a matter of so much discussion here.

The loop is not vented and the non return feature is fine.

b.

Diaphragm pumps and centrifugal pumps are very different. There are also also big differences between centrifugal pumps.

Rule specifically states in their manual for many of their pumps that a check valve must not be used.

page 16
http://www.nhkjab.com/tech/pdf/marin...bmashiburu.pdf

Centrifugal pumps don't develop a lot of pressure, and a lot less if there is air trapped in the impeller. A check valve with water on top of it provides significant back pressure and can prevent the pump from clearing the air from the impeller, keeping it from pumping.

Some bilge pump brands recommend a check valve. I assume they have some way of preventing air locks.

Self priming centrifugal pumps (trash pumps commonly) have an air-water separator.

How a Self-Priming Pump Works | PumpStoreUSA.com

[Hudson Force]

Originally Posted by barnakiel

The vented ones are only used for below water outlets like toilets or raw water inlets on engines.

Bilge pumps normally have outlets above water plane. Hence the loop, NON vented one. .......................
............................

This is generally very reasonable, but the question arises when a effluent above the water can become temporarily below during a sustained heel. I had another event that caused me to add a vented loop to my bilge pump outflow. My bilge outflow through-hull is only a couple inches above my waterline and I found that in a rolling anchorage my bilge pump was frequently cycling on. It turned out that I was taking a sip of water with each roll. Of course a higher loop without the vent could have solved my problem, but I went with the vent. My only vent failure, one in 44 years aboard, was with the vent stuck open and spritzing a salt spray in my engine room. This was troublesome, but not dangerous for anyone keeping and eye on things.

I'm all for not having the check valve in the bilge pump plumbing, but simple loop, vented loop, open high center vent, etc. are all choices that seem to fit upon design and variations in risk management.

[barnakiel]

Originally Posted by Hudson Force

This is generally very reasonable, but the question arises when a effluent above the water can become temporarily below during a sustained heel.(...)

Yes. You are right.


Some solutions I have seen deployed:

- reef, do not sail her on her ear,
- have the bilge pump outlet NOT at the beam (I mentioned this one early on, overlooked by most posters/readers),
- employ a check valve,

Having a vented one does not help when heeled all the way to the rail. Many UK build small boats not just heel to the rail they actually sail with part of the lee deck submeged. A vent will get submersed just as much as the outlet. However, UK builders are smart people and they know the fact that the main bilge is midships does not imply the outlet must be at the beam - they all have the outlets well aft of the beam and so no devices other than plain loop all the way to the deck and back is all it takes to sail with dry bilges.

Simply, if your bilge pump outlet is regularly under water ... maybe it should be elsewhere? If we insist it is where it is, we employ a check valve.

b.

[Dockhead]

Originally Posted by barnakiel

. . .
Simply, if your bilge pump outlet is regularly under water ... maybe it should be elsewhere? If we insist it is where it is, we employ a check valve.

Or leave the sea cock off.

But I do beg you to think again about the check valve. Fine for a diaphragm pump, fine for a maintenance pump, but can terribly degrade the performance of a centrifugal pump designed to move water, which are very sensitive to any restriction in the discharge. Also check are prone to clogging and malfunction -- no tragedy with a toilet, but tragedy if it happens when you really, really need for the bilge pump to move a lot of water. Even a small clog can cause a centrifugal pump to fail to move water. It's not an accident that Rule and others tell you categorically NOT to use a check valve.

[jongleur]

Does anybody have their bilge discharge
into their cockpit? Would act as a siphon
break and let you know if the bilge pump
is running.

[Terra Nova]

More misinformation. NEVER install a check valve in a bilge pump line.

[barnakiel]

Originally Posted by cal40john

Diaphragm pumps and centrifugal pumps are very different. There are also also big differences between centrifugal pumps.

Rule specifically states in their manual for many of their pumps that a check valve must not be used.

page 16
http://www.nhkjab.com/tech/pdf/marin...bmashiburu.pdf

Centrifugal pumps don't develop a lot of pressure, and a lot less if there is air trapped in the impeller. A check valve with water on top of it provides significant back pressure and can prevent the pump from clearing the air from the impeller, keeping it from pumping.

Some bilge pump brands recommend a check valve. I assume they have some way of preventing air locks.

Self priming centrifugal pumps (trash pumps commonly) have an air-water separator.

How a Self-Priming Pump Works | PumpStoreUSA.com

+++ Yes.

Off course.

And when the pump is of the centrifugal style, why does the builder (of the boat) place the outlet at a place that allows for frequent flooding?

I read and understand what people are saying in this thread. What I do not understand is why in our 1967 designed very small boat that does stand a good chance of getting pressed all the way to her rail (only 2 ft of free board here) we have never ever had the bilge hose flood the bilge. Well, I do, the answer is very simple - that naval architect back in 67 knew that the outlet of the bilge is supposed to be where the water normally does not reach, and then he added that little plain non vented loop, just in case we end up on our side anyways.

It is easy to add some good money (a non return valve) to a pile of bad money (poorly designed boat). But it is equally easy to move the outlet to a place where the return non return vented or not dilemma simply stops existing.

We might be at times looking for solutions of problems by adding more problems. Endowment effect I think they call it. Perhaps we have alternatives better than valves and vented loops.

b.

[barnakiel]

Originally Posted by Terra Nova

More misinformation. NEVER install a check valve in a bilge pump line.

What type of pump is it? Centrifugal? Diaphragm? Other?

Why "NEVER"? This is a very broad qualifier. C'mon, give us a chance.

b.

[Terra Nova]

N.E.V.E.R.

[Cheechako]

The bottom line is if you have a big loop aft just before an above water exit fitting, all will be fine....99.999% of the time.
Check valves can effect centrifugal bilge pumps for sure, they don't make much pressure, just volume.... so they don't like back pressure. I tried to put a nice bronze check valve in a BP hose once, I ended up having to put it in the horizontal run of the hose as in a vertical run it created too much back pressure on the pump from the heavy bronze flapper in the valve.

[barnakiel]

Originally Posted by Dockhead

Or leave the sea cock off.

But I do beg you to think again about the check valve. Fine for a diaphragm pump, fine for a maintenance pump, but can terribly degrade the performance of a centrifugal pump designed to move water, which are very sensitive to any restriction in the discharge. Also check are prone to clogging and malfunction -- no tragedy with a toilet, but tragedy if it happens when you really, really need for the bilge pump to move a lot of water. Even a small clog can cause a centrifugal pump to fail to move water. It's not an accident that Rule and others tell you categorically NOT to use a check valve.

I 100% agree with this.

(Maybe not all that much with the part "no tragedy with a toilet" ;-)

Avoid check valves (non return valves) in centrifugal bilge pumps installation.

Check pump valves are not required in properly installed bilge pump runs.

Properly installed bilge pump runs exclude beam location of the outlet in boats that sail with their rail in the sea.

To me, it sounds like we are all talking of the same thing, just the angles we have are the ones induced by the boats we are in.

Give me another boat and I will start loving vented loops in toilet outlets, vent inside ;-)

Still, some of us are about to grab a big drill, some 3M goo and move that bilge outlet thru-hull to an alternative location. Maybe.

b.

[Cheechako]

http://www.starmarinedepot.com/whale-inline-non-return-valve-1-1%2F2/pzz19518.html?gclid=CjwKEAjw0KK4BRDCiKHD5Ny8pHESJA CLE620zT5LCjJj5pGPmMzVR4yw4J3eTOhhggvOc1C1TwJ82BoC Kmvw_wcB
https://www.zoro.com/jabsco-in-line-non-return-valve-1-12-in-29295-1010/i/G0667931/?gdffi=047ada998cf641fa93e55ae8579df863&gdfms=4D16 E42430D04E598669CC0B68DF1F59&gclid=CjwKEAjw0KK4BRD CiKHD5Ny8pHESJACLE620SV9CvAylAi46kTnguAO_7l-JJZSh6MEYUay_A_ZwQhoCz9Hw_wcB&gclsrc=aw.ds

[barnakiel]

Originally Posted by Terra Nova

N.E.V.E.R.

Eh, Y.O.U. ...

;-)

Now that I have read your three most recent posts I am beginning to understand there is no need for more opinions. Never implies never just like the fact that someone does make an effort of saying something thrice implies others should think thrice before asking further questions.

So let me just confirm that I will NEVER install one since I NEVER have one NEVER need one.

I EVER admire your sense of humour even though I NEVER always get it before you express it thrice.

Which makes me wonder if the fact that I admire your boat so much has anything to do with how much I am willing to re-read my own posts and re-think my own attitudes to find where I said something stupid.

It sucks we live so far apart as I would love to have a beer with many of the forum, much as I understand they could just as well refuse. ;-)

+Big sunny hug,
barnakiel