Pumping shower water overboard

[Scary]

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 .

 

[yo]

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

 

[meridian]

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.

 

[psneeld]

This is not a serious post, right?

Actually completely serious....

 

[Capt.Bill11]

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?

 

[markpierce]

I like the idea of having the shower water pumped to the sink drain whose thru-hull is above water

 

[SCOTTEDAVIS]

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.

 

[High Wire]

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.

 

[Scary]

Head pressure isn't effected by volume

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.

 

[Art]

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!!!

 

[Britannia]

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

Richard

 

[Britannia]

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.

 

[Art]

I never before thought that draining shower water from a boat would create such a rocket science discussion.... Geeeezzzz!

 

[N4712]

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.

 

[HopCar]

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.

 

[Britannia]

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.

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...

Richard

 

[Art]

S / P flow down hill, can be pumped in any direction... and ... don't bite your fingernails!!

 

[Peter B]

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.

 

[Peter B]

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".

 

[Marin]

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.

 

[markpierce]

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."

 

[Peter B]

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..?

 

[kulas44]

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.

 

[twistedtree]

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.

 

[psneeld]

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.

 

[Nomad Willy]

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.

 

[bligh]

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.

 

[Northern Spy]

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.

 

[markpierce]

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.

 

[ranger58sb]

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?

-Chris