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Old 05-16-2015, 12:03 PM   #21
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My shower water runs into the bilge. The yardmaster says the shower-sump pump doesn't have the power to push water through the thru-hull which is a couple inches below waterline.
Others nailed it with a check valve your pump cannot overcome the back pressure of to drain. You stating it works fine hauled confirms the problem is back pressure and nothing else.

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He's suggesting creating an above-water-line thru-hull to correct the problem. What are your thoughts?

Completely agree with his suggestion. Be sure a loop of hose above the sea cock is present when job is complete.

Now, about this sump box that is not water tight....
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Old 05-16-2015, 12:16 PM   #22
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It is utterly disgusting to pump shower water overboard in areas others may use that water....for swimming and such...as fecal matter does go into the shower sump more than occasionally.

For gosh sakes...it is way less sanitary than elcectroscan waste water.

I suggest leaving it in your own boat and having a pump out dispose of it.
This is not a serious post, right?
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Old 05-16-2015, 12:23 PM   #23
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Others nailed it with a check valve your pump cannot overcome the back pressure of to drain. You stating it works fine hauled confirms the problem is back pressure and nothing else.




Completely agree with his suggestion. Be sure a loop of hose above the sea cock is present when job is complete.

Now, about this sump box that is not water tight....
Good suggestions.

It is also possible the the power of the pump cannot exceed the inertia of pumping into water as opposed to pumping into air.

Mark the first thing I would check is the sizes of the drain hose and the through hull. ( what size is the through hull?) It is possible that the pump cannot overcome the head pressure through the hose and fittings (and check valve if present) sufficiently to keep up with the water flow of the shower head. You may solve your problem by just installing larger hoses on the interior of the system which will significantly lower the head pressure and increase flow (GPM). Worst case, you will have to do what the yard suggests. You could also try using a shower head with a lower GPM so the pump can keep up with it. However, it does seem odd that the shower sump is below the water line since its a sump line.
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Old 05-16-2015, 12:47 PM   #24
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I'm having a hard time with the idea that drilling a hole in the hull is a good solution for an underpowered pump. I don't agree that the current design is unworkable. I don't like the idea of a simple check-valve as opposed to a loop and anti-siphon valve.

There is another alternative. Do you have a sink close by to the sump pump? In my sailboat the sump pump is connected to the drain hose from the head sink (at a point above the waterline). When it pumps, the sump water backs up into the sink which acts as a holding tank while the water drains through the sink's thru-hull. The amount of water is never enough to overfill the sink. A quick rinse of the sink afterwards is all that is needed. The sink acts as the anti-siphon valve. It's crude but effective.

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Old 05-16-2015, 01:17 PM   #25
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Mark, do you have a vented loop to keep water from back syphoning into your bilge. It seems that you are dependent upon one check valve that could easily malfunction and sink the Coot. I would cap off the existing thru hull fitting until used for an intake later.

Shower water has hair and human skin cells as well as other organic matter. It should not drain into the bilge. Over time sewer odors would be evident.
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Old 05-16-2015, 01:59 PM   #26
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Good suggestions.

It is also possible the the pewr of the pump cannot exceed the inertia of pumping into water as opposed to pumping into air.

Mark the first thing I would check is the sizes of the drain hose and the through hull. ( what size is the through hull?) It is possible that the pump cannot overcome the head pressure through the hose and fittings (and check valve if present) sufficiently to keep up with the water flow of the shower head. You may solve your problem by just installing larger hoses on the interior of the system which will significantly lower the head pressure and increase flow (GPM). Worst case, you will have to do what the yard suggests. You could also try using a shower head with a lower GPM so the pump can keep up with it. However, it does seem odd that the shower sump is below the water line since its a sump line.

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?
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Old 05-16-2015, 02:02 PM   #27
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...It seems that you are dependent upon one check valve that could easily malfunction and sink the Coot...
My concern too.
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Old 05-16-2015, 02:07 PM   #28
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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?
No - static pressure is only dependent on the "head" of water above the point pressure is being measured, whether that's a 1" hose or the entire ocean. Flow rate is another thing though - and for a pump to increase its flow rate through a narrower hose it has to increase pressure. So a wider hose may help the flow rate but shouldn't make any difference to the ability for the pump to pump. At some point, with a long enough and narrow enough piece of hose that friction in the tube may become a factor. I doubt it's significant in this case.

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Old 05-16-2015, 03:34 PM   #29
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Thanks for all the suggestions. I'll discuss them with the yard.
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Old 05-16-2015, 03:49 PM   #30
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Thanks for all the suggestions. I'll discuss them with the yard.
There is something just not to design specifications...that said, my suggestion is to contact the builder. They should know the boat and setup better than anyone. I would email Seahorse before doing anything.
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Old 05-16-2015, 03:52 PM   #31
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keep it simple

I don't like the idea of using the bilge as a sump. Human hair, soap and waste are pretty unsavory, you never know what a guest who is used a home shower may do. A though below the waterline needs a shutoff and vented loop if the sump is below the water line. Why not install a above waterline through hull and a automatic submersible bilge pump in a covered sealed battery box.I use a heavy duty 8d battery box and bilge pump with a float switch .
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Old 05-16-2015, 05:04 PM   #32
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do the same thing that is done at your kitchen at home tap into your sink drain same as your dish washer. Tap into you bath room sink drain on the boat, same y fitting as used at you home
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Old 05-16-2015, 05:09 PM   #33
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I got rid of my sump box and 10 feet of 30 year old drain hose, purchased a small shower sump box and "T" it into the sink drain. No loop required as the outlet is above the water line.
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Old 05-16-2015, 05:17 PM   #34
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This is not a serious post, right?
Actually completely serious....
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Old 05-16-2015, 05:31 PM   #35
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No - static pressure is only dependent on the "head" of water above the point pressure is being measured, whether that's a 1" hose or the entire ocean.
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?
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Old 05-16-2015, 06:07 PM   #36
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I like the idea of having the shower water pumped to the sink drain whose thru-hull is above water
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Old 05-16-2015, 08:36 PM   #37
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Actually completely serious....

I bet the folks you are worried about swimming in the anchorage that my shower water is draining into are doing a bit more then I do in my shower, ya think?

The Pilgrim's shower floor is above the water line by a good 12 inches so it just drains out like the sink, no pumps or sump.
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Old 05-16-2015, 08:45 PM   #38
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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?
Static head pressure is a function of only the difference in height and the density of the fluid. It could be a 1/4" diameter sight glass, 2" diameter hose, or 20 feet diameter as in a storage tank. 5 feet of height of water results in .433 psig per ft = 5 x .433 = 2.165 psig. This assumes the column of water is above the measuring point. It gets more complicated if the column starts below the measuring point or the fluid is flowing.

A classic example is the sight tube on the side of a diesel fuel tank. Both vented and valved in. The fuel tank has more mass and weight than the fluid in the sightglass, but the static pressure at the bottom glass fitting is exactly the same on the tank side and therefore indicates an accurate tank level.
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Old 05-16-2015, 11:16 PM   #39
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Head pressure isn't effected by volume

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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?

Head pressure is not a factor of volume. Height is the determining factor. The pressure at 16' in the ocean is the same as 16' in a 1" pipe. That would like saying swimming in a pool at 16' would be different than swimming in the ocean at 16'. If the hose was undersized there would be added resistance because of drag and restricted volume which would increase pressure when the pump was running. So it is possible to increase pressure if the pipe is too small for the volume of water it can pump. Usually the pump outlet determines the size of the hose. If the hose is larger than the outlet velocity the water will slow until restricted again. Like putting your finger over the end of a garden hose.
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Old 05-16-2015, 11:22 PM   #40
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It is utterly disgusting to pump shower water overboard in areas others may use that water....for swimming and such...as fecal matter does go into the shower sump more than occasionally.

For gosh sakes...it is way less sanitary than elcectroscan waste water.

I suggest leaving it in your own boat and having a pump out dispose of it.
Yeah...and... no peeing while swimming!!!
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