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Old 05-16-2015, 11:32 PM   #41
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Originally Posted by Capt.Bill11 View Post
That's my point. Going to a larger diameter hose will not lessen the head the pump sees.

But if it is pushing up against a say 4 foot vertical column of water in a 3/4" hose it can't be the same as pushing against a column of water in a 2" hose. The water in the 2" hose has more mass thus more weight, no?
No.

Here's the easiest way to think of it. Let's suppose the pump needs to pump one pint of water. Let's suppose that the narrow hose holds one pint of water in 4 feet. Then the pump needs to move the column of water up 4 feet. Now suppose that a larger hose is used - with twice the diameter and hence four times the cross-sectional area. Now the pump only needs to move the wider column of water up 1 foot to pump the same pint of water. So it moved 4 times as much water up 1/4 of the distance. So the same work was done by the pump in both cases - and it is not affected by the diameter of the hose (ignoring friction).

I hope that helps

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Old 05-16-2015, 11:34 PM   #42
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I like the idea of having the shower water pumped to the sink drain whose thru-hull is above water
Yep - that's how my sailboat is set up. Simple reuse of an existing thru-hull - and the sink drain hole creates an anti-siphon valve.
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Old 05-16-2015, 11:51 PM   #43
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I never before thought that draining shower water from a boat would create such a rocket science discussion.... Geeeezzzz!
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Old 05-17-2015, 12:00 AM   #44
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I never before thought that draining shower water from a boat would create such a rocket science discussion.... Geeeezzzz!

Exactly What I'm thinking right now reading through this thread.
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Old 05-17-2015, 12:07 AM   #45
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Knowing how all of the other systems on Mark's boat are so well thought out, I'd bet on a pump that has gone bad, rather than a badly designed system. I have to admit, I wouldn't put a sump and the discharge both below the waterline.
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Old 05-17-2015, 12:10 AM   #46
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I never before thought that draining shower water from a boat would create such a rocket science discussion.... Geeeezzzz!
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Exactly What I'm thinking right now reading through this thread.
Sorry - stop reading if you're head's spinning.

Physics is all around us

And after all - it is actually useful to know that a larger hose won't require a bigger pump...

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Old 05-17-2015, 12:30 AM   #47
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S / P flow down hill, can be pumped in any direction... and ... don't bite your fingernails!!
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Old 05-17-2015, 01:54 AM   #48
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Thanks for all the suggestions. I'll discuss them with the yard.
Mark, I'm sorry I have not had time to read all the posts on here, so apologies to you and any if I just duplicate what some have already said, and I am only posting because your query was one I had to address myself. In our boat the shower waste does just run into the small forward bilge and is pumped out by the automative bilge pump. Our bilge is not one you could eat your breakfast out of anyway, so I lose no sleep over it, and by using low residue shower soap, (Dove to be precise) it is simple, works well, and is damn near foolproof, so FF has a supporter here. The only downside to this is if your marina insists on a bilge outlet filter, in which case the shower waste will clog the filter a bit sooner than otherwise.

However, the man who surveyed our boat was himself a live aboard, (GB 32), and we got discussing the issue, and the scenario he described as "the best', was to have a shower sump, which you have, and a manual switch powering a Whale Gulper (diaphragm type) pump, which will never block with hair etc, and it must go to an above waterline thru-hull. You just turn it on when you start showering. It is not damaged by running dry anyway. No valves needed.

Your arrangement sounds potentially dangerous, (as others have mentioned), unless you are closing a seacock in the line after each use. So that below waterline discharge surely must go. So if you can use Brittania's idea of y-connecting it into the sink drain, all the better - no new hole needed. Anti-siphon effect provided free.

If I've just corroborated what some others have said, then all the better.
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Old 05-17-2015, 02:12 AM   #49
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Yeah...and... no peeing while swimming!!!
My mother used to explain the pronunciation of words like phenomenon (with a smile, I might add), by saying "the pee is silent as in psea bathing".
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Old 05-17-2015, 02:21 AM   #50
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The only difference between the system Peter describes for the GB32 and the system on our boat is the pump used. The Whale Gulper is an excellent choice for this service. Our boat was fitted with a pump called-- I think-- a peristatic pump, which is like a blood transfusion pump in having rollers that run round the inside of a circular chamber and compress a rubber tube that has the material being pumped inside it. I suspect the thing will pump wet sand, but when it craps out we'll replace it with a Whale.
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Old 05-17-2015, 04:29 AM   #51
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Here are the two approaches suggested by the builder:


"It looks like the pump can't compress the air column in the outlet enough to force the water out near the thruhull. An easy fix is a "T" at the top of the loop to let the air out as the pump water goes up the hose and as it flows down to the thruhull the remaining air will escape. The vent hose has to go high enough to not allow the pressure to push water up and out. About 2 feet if possible. Or "T" the vent in the sink drain with a loop."
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Old 05-17-2015, 06:30 AM   #52
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What was their view of the underwater thru-hull tho Mark..? Weren't they concerned re back flow, siphoning, especially as your sump pump reservoir is not a sealed unit, and presumably there is no seacock, or if there is it is hardly practical to close it after every shower..?
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Old 05-17-2015, 08:24 AM   #53
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I'm with Phil on this one. and yes, I've always "read" that its a bad idea, stinks, worst possible thing you could do, etc. My experience does not bear that out. My forward bilge in the sporty is not huge and its seperate from the rest of the boat so shower water isnt everywhere. It has 3 pumps in it, a 2500 gph crash pump, a regular 1100 gph automatic bilge pump and a Jabsco diaphram bilge pump. I use WaterWitch electronic switches that incoorporate a shutoff delay that keeps the Jabsco running a while longer. It gets just about every bit of water possible out of the bilge. It helps that the pickup point is in the lowest part of the V. The Jabsco pulls thru a Perko 1 inch strainer, I clean it maybe once a year.
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Old 05-17-2015, 09:57 AM   #54
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Not much discussion so far about the importance of a vented loop. Or maybe you already have one and I missed it?

Regardless of the position of the thruhull, I would think the sump should pump up well above the waterline, then flow down to the thruhull. This is especially important with below or at-water-level thruhull to prevent siphoning back into the boat.
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Old 05-17-2015, 10:13 AM   #55
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There are numerous possible installs...without an accurate drawing including heights above waterline, types and sizes of pumps and hoses....guesses and dissing others opinions are all comical.


Only half the possible install require above waterline fittings, vented loops, more powerful pumps...etc..etc..


Start with a deign you are willing to live with and add the appropriate (and fully working) components to make it work and work safely.


Guessing about pieces and parts is a waste of time.


Mark...pics with notations and or drawings would be the biggest help...the biggest issue is where all the parts are in relation to the waterline.
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Old 05-17-2015, 10:41 AM   #56
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Re psneeld's sani post,
The solution to pollution is dilution.
It worked much better in Alaska that it would down here in Washington.
Just too many people down here.
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Old 05-17-2015, 11:51 AM   #57
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Quote:
Originally Posted by Capt.Bill11 View Post
How would bigger hoses increase the output of a pump passed it's rated output or change the head pressure it sees?

If it's let's say, trying to pumping up vertically 4 feet with 3/4" hose, how does that rise change if you switch to 1 1/2" hose?

Wouldn't 1 1/2" hose hold more volume of and thus weight of water making it even harder for the pump to over come it?
Friction loss of small diameter pipes compared to large diameter pipes measured as ft of head loss. It can be rather significant for smaller pumps.
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Old 05-17-2015, 12:20 PM   #58
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Quote:
Originally Posted by markpierce View Post
Here are the two approaches suggested by the builder:

"It looks like the pump can't compress the air column in the outlet enough to force the water out near the thruhull. An easy fix is a "T" at the top of the loop to let the air out as the pump water goes up the hose and as it flows down to the thruhull the remaining air will escape. The vent hose has to go high enough to not allow the pressure to push water up and out. About 2 feet if possible. Or "T" the vent in the sink drain with a loop."
Yes. Venting the loop is important as it prevents the loop to reverse syphon SF Bay back into your shower.

If the loop is merely hose, than placing a tee would work as long as the tee is vented to an appropriate place at a higher elevation. Teeing the vent to the sink drain can work as long as you don't inadvertantly drain the sink into the shower sump. Ensure something like a sanitary tee or a wye is used. You can also purchase a vented loop, which will have a duckbill valve on the extrados at the top of the loop. Sometimes these may not work so well as they can get plugged with debris. If one is installed make sure you can access the duckbill valve easily enough for periodic cleaning.
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Old 05-17-2015, 02:11 PM   #59
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What was their view of the underwater thru-hull tho Mark..? Weren't they concerned re back flow, siphoning, especially as your sump pump reservoir is not a sealed unit, and presumably there is no seacock, or if there is it is hardly practical to close it after every shower..?
The shower drain line is routed above waterline before dropping to the below-waterline thru-hull. I normally keep the thru-hull valve closed.
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Old 05-17-2015, 03:06 PM   #60
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Here's the easiest way to think of it. Let's suppose the pump needs to pump one pint of water. Let's suppose that the narrow hose holds one pint of water in 4 feet. Then the pump needs to move the column of water up 4 feet. Now suppose that a larger hose is used - with twice the diameter and hence four times the cross-sectional area. Now the pump only needs to move the wider column of water up 1 foot to pump the same pint of water. So it moved 4 times as much water up 1/4 of the distance. So the same work was done by the pump in both cases - and it is not affected by the diameter of the hose (ignoring friction).

But if the pump is here, the thru-hull is there, and the distance is X feet... the pump still has to move the water X feet, yes?

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