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Old 17-10-2015, 20:47   #1
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Sink drain & bilge pump, same discharge?

Hello friends,

I have been trying to square away my plumbing while at work so when I get off the ship I can knock it out quickly. I am racking my head over this and didn't find much online regarding this so I'm asking you people for guidance.

To start off, let me tell you what I'm working with. Under my galley sink(and the two head sinks too) Redemption has three seacocks, a 3/4", 1", and a 1.25". As it stands now, I have a Whale Gulper hand bilge pump going to the 1.25. The other two I have been trying to figure out.

I have a sink drain, a footpump for S/W, and a 1500gph auto bilge pump that need thru hull services. I was going to put the foot pump on the 3/4" for water conservation uses. The other two I was planning on using the 1" seacock with a "T" fitting that would be on its side. The top would have the bilge pump plumbed to it with a vented loop. And the side hole would be for the sink drain.

Is this possible? I have honestly thought myself numb. I have read that people put the head sink drain on the toilet intake seacock with a "T" fitting. The only difference I see is the toilet is a suction and the bilge pump is a pressure.

I'm attaching a lovely, professional diagram of the setup I'm talking about for purposes of everyone being on the same page. Click image for larger version

Name:	uploadfromtaptalk1445136387470.jpg
Views:	477
Size:	278.7 KB
ID:	111152

A side note, all of my thru-hulls are Below the waterline save for two 2" cockpit drain holes.

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Old 17-10-2015, 22:00   #2
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Re: Sink drain & bilge pump, same discharge?

That will work fine. The 1500 gph bilge pumps rating is based on zero feet of head. It looks good for marketing that way. But there is always head loss. Real world performance will be a wee bit less. With the hose loss, pump inlet loss, etc, your probably looking at somewhere around 12 ish gpm (750 ish gph) which is easily doable for a 1" connection. In theroy it would be find for 20 GPM, but 12V bilge pumps are generally not very efficient, so peak flow rate in real world installations will be maybe 50-60%, of the manufacture rating.
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Old 18-10-2015, 01:58   #3
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Re: Sink drain & bilge pump, same discharge?

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Originally Posted by sailorchic34 View Post
That will work fine. The 1500 gph bilge pumps rating is based on zero feet of head. It looks good for marketing that way. But there is always head loss. Real world performance will be a wee bit less. With the hose loss, pump inlet loss, etc, your probably looking at somewhere around 12 ish gpm (750 ish gph) which is easily doable for a 1" connection. In theroy it would be find for 20 GPM, but 12V bilge pumps are generally not very efficient, so peak flow rate in real world installations will be maybe 50-60%, of the manufacture rating.
So I can put the sink drain and the bilge pump on the same seacock by way of a "T" fitting?

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Old 18-10-2015, 04:21   #4
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Re: Sink drain & bilge pump, same discharge?

Yes, it will work. Some things to consider:

Make sure your vented loop is above the waterline at all points of sail. Otherwise, water will flow through and fill up the bilge. Likewise, make sure that your sink, even if you have it fairly full of water, won't empty through the bilge pump into the bilge. Centrifugal pumps allow back flow of water.

I like having the bilge pump discharge higher so that I can see and hear when the bilge pump is on. Since your discharge will be below the waterline, it would be nice to have some means of alerting you when the bilge pump is running. We have an Aqualarm smart bilge monitor which alarms if the pump runs more than two minutes.

With the sink drain going to a 1" hose and through hull, are you concerned with debris causing blockage over time? Perhaps you could use the 1-1/4" through hull for the sink drain/bilge pump discharge, and the 1" for the manual bilge pump.

Cheers!

Steve
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Old 18-10-2015, 09:10   #5
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Re: Sink drain & bilge pump, same discharge?

I have a similar discharge configuration. Many times but not always, when the pump comes on line, the sink drain will burp up a 1/4 cup of bilge water into the sink before it starts flowing overboard. Because of this, I leave the stopper in the sink.
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Old 18-10-2015, 09:11   #6
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Re: Sink drain & bilge pump, same discharge?

Quote:
Originally Posted by SailRedemption View Post
Hello friends,

I have been trying to square away my plumbing while at work so when I get off the ship I can knock it out quickly. I am racking my head over this and didn't find much online regarding this so I'm asking you people for guidance.

To start off, let me tell you what I'm working with. Under my galley sink(and the two head sinks too) Redemption has three seacocks, a 3/4", 1", and a 1.25". As it stands now, I have a Whale Gulper hand bilge pump going to the 1.25. The other two I have been trying to figure out.

I have a sink drain, a footpump for S/W, and a 1500gph auto bilge pump that need thru hull services. I was going to put the foot pump on the 3/4" for water conservation uses. The other two I was planning on using the 1" seacock with a "T" fitting that would be on its side. The top would have the bilge pump plumbed to it with a vented loop. And the side hole would be for the sink drain.

Is this possible? I have honestly thought myself numb. I have read that people put the head sink drain on the toilet intake seacock with a "T" fitting. The only difference I see is the toilet is a suction and the bilge pump is a pressure.

I'm attaching a lovely, professional diagram of the setup I'm talking about for purposes of everyone being on the same page. Attachment 111152

A side note, all of my thru-hulls are Below the waterline save for two 2" cockpit drain holes.

Sent from my VS986 using Tapatalk
You can do it, (you CAN do anything) but not recommended.

1. This is not ABYC compliant. (An astute surveyor should call it for insurance or pre-purchase survey when you sell.)

2. There should be no extra fittings (than necessary) in a bilge pump line. I

3. Bilge pumps are better without a vented loop if you can make the discharge above the heeled waterline.

4. If the sink drain plugs due to grease, hair, etc. the boat may sink if the bilge pump is connected.

5. Reducing the bilge pump discharge line will reduce its output.

6. Knowingly reducing the effectiveness of you bilge pump is not very prudent seamanship.

7. If this would allow you to install another high capacity bilge pump (with separate dedicated discharge) then that would be a consideration.

8. Doing this just to reduce the number of thru-hulls, is NOT a good idea.

The following are excerpts from my marine electrical seminar, which includes a fair bit of detail about bilge pumps (one of the most poorly selected, poorly installed, and poorly maintained items I find on most boats.)

9. The bilge pump(s) on most boats are only suitable to remove incidental leakage. With a serious hole (2" in diameter, 1 foot below the waterline), most will most definitely sink. A good rule of thumb is to have at least 1000 GPH of auto electric bilge pump (installed to give as close to its performance as possible, an none greater than 2000 GPH) for every 8 ft of boat length.

10. Lastly, what few people consider, if you every discover you do have a catastrophic leak under way, as soon as practical, start the engine. (The increased supply voltage (14.2 instead of something less than 12.8) will increase the bilge pump(s) output, giving you more time to find and repair the leak, before the batteries are covered, the pumps quit, and the boat goes down.

If you can't keep the water from getting to the top of the batteries, or before that the bilge pumps stop (due to poor installation practices), and you haven't done so all ready, get the ditch kit and life raft or dinghy ready. Keep trying with a bucket until help comes or you have step up into the life raft.

(Don't bother trying to epoxy a huge gaping hole with no backing as in the movie "All is Lost" as we saw what happened to that boat.)

Ramblin Rod
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Old 18-10-2015, 09:36   #7
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Re: Sink drain & bilge pump, same discharge?

After thinking about this, I am going to change my mind and say it probably will not work. I believe that when your bilge pump comes on, it will immediately begin pumping water faster than it can drain out the 1" through hull. The water will back up into the sink.

With the sink open to atmosphere, you no longer have pressure from the bilge pump discharge. All you will have is a gravity drain from the water in the hose.

In a case where you need to pump a lot of water due a leak, I'm afraid you will find that the 1500 gph pump will only move less than two gallons a minute overboard, with the rest just going up the sink drain until it overflows, putting water back into the bilge.

Cheers!

Steve
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Old 18-10-2015, 09:58   #8
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Re: Sink drain & bilge pump, same discharge?

I would say it it would work ok, although not ideal.

I don't see anything in the ABYC standards on bilge pumps that says this would not be compliant. The only reference to discharge line is that it "shall be as non-restrictive as practicable" It also states that "multiple pumps or manifolding may be used"
https://law.resource.org/pub/us/cfr/....H-22.1986.pdf

Yes - I agree that there is a small increased risk of blockage from crap down the sink drain, so separate seacocks are better, but is it practical to use your 1 " seacock?
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Old 18-10-2015, 11:32   #9
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Re: Sink drain & bilge pump, same discharge?

Quote:
With the sink open to atmosphere, you no longer have pressure from the bilge pump discharge. All you will have is a gravity drain from the water in the hose.
My thoughts are the same, the admittedly minimal pressure developed by the bilge pump will be lost at the Tee and it's gravity flow from there. An air tight stopper in the sink drain would help but some pressure would be lost in compressing the air trapped in the drain line. I'm a little fuzzy regarding what you have available but a thru hull devoted to the bilge discharge would seem a better option if available.
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Old 18-10-2015, 12:32   #10
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Re: Sink drain & bilge pump, same discharge?

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5. Reducing the bilge pump discharge line will reduce its output.

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1500 gph Rule pump has a 1 1/8" output. Rule's 2000 gph pump has the same size output. Output should not be reduced.

I would use a dedicated above the waterline through hull for a bilge pump though. I don't think a bilge pump's output should be T'd into any other hose - including that of another bilge pump.
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Old 18-10-2015, 12:59   #11
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Re: Sink drain & bilge pump, same discharge?

People do bizarre things when they are a little weak on the fundamental concepts. When TrentePieds came to us, the ice-box drain was taken to the hose of the two forward cockpit scuppers that exited BELOW the water line via a seacock.

The after scuppers drained, as they should do, above the water line. But they are 2 inches above the forward scuppers when TrentePieds is in normal trim

Thus, when it rained and the seacock for the foward scuppers was closed as it should be, the rainwater backed up into the icebox!

As for bilge pumps, it's not unusual for people to believe that the purpose of those deekie little submerged Rule pumps with the float switches are there to save you when the ocean really wants to come in. Re-education is required! I don't know of any pump that will do that.

For what they the common run of bilge pumps CAN do, they are fine. But absolutely nothing else should be taken to their outlet hoses, and a riser with syphon break should always be provided

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Old 18-10-2015, 15:39   #12
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Re: Sink drain & bilge pump, same discharge?

Thanks for the replies friends. I have mulled over your responses and thought it over. At first I thought, well I could T the 1.25 seacock for the sink and hand pump since that is a last resort type pump anyways, I could plug the sink drains to keep pressure. BUT, that didn't sit with me AND it's already hooked up so that's out.

What I think I can do, since I can put the aft head, which is just across the centerline from the galley, sink drain on the toilet intake, that will free up a 1" thru hull (remember I have the same set of valves under each sink). This would allow me to pump the bilge pump (Marpac 1500gph, has a 1 1/8 or 1 1/4 hose) to that 1" seacock with a 1" npt - 1 1/4" fitting(with a vented loop of course).

Through insight from you lot, we have figured it out I believe. Now I just have to figure out how to turn the pump around since the base plate was epoxied to the bilge bottom. And routing the hose...

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Old 18-10-2015, 17:49   #13
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Re: Sink drain & bilge pump, same discharge?

I would also never want a bilge pump outlet to be below the waterline. On a sailboat the best location is the transom, with the sides at the stern a second choice. About halfway between the waterline and deck with an anti-siphon loop under the deck.

There are pumps that can save a boat but as posted 1500 gph units won't.

Pacer Pumps
Flow rate up to 280 gpm (that's minute).
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Old 19-10-2015, 01:32   #14
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Re: Sink drain & bilge pump, same discharge?

Whichever way you go, test out your bilge pump capability before you need it.

Remove the hose from your largest thru-hull, open the seacock and let the water flood your bilge. Monitor it and see if the pump will handle the water volume. My 1500 GPH pump handles a 1 " thru-hull inflow, running about 50% of the time. I'm ok with that, but still plan to install another backup pump at a higher level (to be sure to be sure).

Every bilge pump output will be different depending on the depth of your bilge, the size, length and type of discharge hose, the height of your outlet, the configuration of fittings, power supply etc.
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Old 19-10-2015, 02:10   #15
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Re: Sink drain & bilge pump, same discharge?

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Whichever way you go, test out your bilge pump capability before you need it.

Remove the hose from your largest thru-hull, open the seacock and let the water flood your bilge. Monitor it and see if the pump will handle the water volume. My 1500 GPH pump handles a 1 " thru-hull inflow, running about 50% of the time. I'm ok with that, but still plan to install another backup pump at a higher level (to be sure to be sure).

Every bilge pump output will be different depending on the depth of your bilge, the size, length and type of discharge hose, the height of your outlet, the configuration of fittings, power supply etc.
Good idea, I do have another Rule 750gph pump, these two are on a blue seas dual bilge pump 360 auto pump switch separate from the breaker panel straight to the battery. I plan to use an old whale diaphragm discharge pump for a backup manual switch as well hooked up to the breaker panel. I will also be able to use my whale diaphragm shower sump pump in emergency too.

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