Opinions on thru-hull sketch (Houseboat)

This is a rough rendering of my houseboat project: 34' Marinette. 1 thru-hull to drain basin sink and the 2nd to drain shower/drain bildge box and main bilge. Question: would you tie in the main bilge in like that or have a separate thru-hull higher up above water line? On a bigger boat like this houseboat would you have the main bilge pump positioned high up or go with a larger submersible type? Thanks.

 

Actual Sketch of thru-hulls

Sorry about that, here is the actual rendering of the thru-hulls that I was asking for opinions about: http://s1216.photobucket.com/albums...Individual album to exhibit certain pictures/

 

In the case of a house boat i would try to have no holes through the hull at all . Slghtly above is not good enough . Over time when you are least exspecting skin fitting give out hoses rot clips let go and befor you know it Gruggle gurggle you have a problem with water in the hull/s So no hole no way for water to get in !!!

 

Through hulls are instruments of the devil designed specifically to give you unexpected grief. If you must....then keep them as far above the waterline as can be contrived....even if you have to use a dump pump,

 

Why not have the waste dumped from under the bridgedeck? If water comes in there it does not matter then.....

 

Rsimon,

All discharge lines should be placed as far above the waterline as possible. Ideally there are no holes in a boat below the waterline, since this eliminates possible failure points that could sink the boat. It is only intake lines that should be placed below the water.

And each bilge pump should discharge directly overboard by its own fitting and hose. They should never be combined, either together or with other water lines.

As for your bilge system, I always recommend at least two pumps. For the first I use a small diaphragm, self priming pump that can be run dry. This picks up from a hose as low down in the bilge as possible, and operates from a float switch with a time delay. The delay should be timed to run for the period of time from when the switch turns off until all remaining water is removed from the boat.

What this does is remove as much water as possible from the bilge, which isn't really possible with a traditional bilge pump.

The second is a large volume pump sized to remove an amount of water equal to the flow of the largest below the waterline through hull fitting. This can be obtained from http://www.efunda.com/formulae/fluids/draining_tank.cfm . This pump should be at least six inches higher than the float valve for the other pump, and should ideally always be dry. This pump should also be tied to a high water alarm that sounds on the bridge, and in any sleeping quarters.



This system ensures that the bilge keeps dry for normal dewatering which is always good, and that in the event of reasonably forseable emergencies you have enough volume in pumps to give you time to try and correct the problem.

 

Ok, Stumble that helps a lot, thanks... Those 2 thru-hulls are where Marinette put them.
I have not had the boat in the water yet since pulling out 5 years ago to work on this project so I really am not sure if those 2 thru hulls are AT or slightly above the water line.
I will change my plan as to NOT to "T" the bilge line out into thru-hull#2. I assume the second large volume pump would be D/C powered. I was considering a separate high volume pump for a different system (to pull water in from the lake for wash-downs.)
See that concept as well as updates rendering here: http://s1216.photobucket.com/albums/dd377/projecthouseboat/Thu hull 1 and 2 depiction and uses/

 

If you are going to install a wash down pump I would go ahead and add a through hull for it. Preferable by tapping into an intake you already have (heads, or sink are common spots) since an external one is just way too likely to get ripped off.

The concern about through hulls is just that a concern. They should be minimized when you can, but don't take that desire to extremes.

 

It's only practical to say you don't want thru hulls above the LWL. In reality, they are an unfortunate happenstance. You just have to have them and you also just have to assume someone will preform the reasonable maintenance necessary, to keep them from causing issues.

Thru hull failures can be traced back to lack of maintenance 99% of the time. Every so rare occasion, you might find one with an internal flaw, so that it fails unexpectedly, but the sad reality is no one checks them, changes out clamps/hoses, rebeds them, operates the valve or even hangs a tapered plug next to each, until one fails and you have to pump out the old gal.

The bottom line is you can make excuses, about the terrors of thru hulls, or you can accept the responsibility of their care and never have a lick of trouble.

On larger craft you can afford to have a majority of thru hulls, well out of the water, which is safer, especially if you plan to neglect them until they fail. The wise owner routinely checks them, hangs a plug, uses good valves, proper clamping procedures, etc. These thru hulls don't cause problems, regardless of location, because a weeping bedding will be seen as a stain, a cracking hose will be seen before it leaks, a loose clamp will be tightened or replaced, etc., etc., etc. It's only the thru hulls that hang helplessly for years without service or attention that fail.

All of this assumes you haven't bashed one in on a rock or pile or something. Thru hulls well above the LWL tend to have this happen. Someone rafts up along side (or whatever), you have a little party and his rub rail wipes the outer half of your cheapo plastic thru hull, right of the side of your boat, without you knowing it, until the pumps start running continuously.

Thru hulls are necessary and all hull penetrations need to be taken seriously. They're nothing to fear or worry about, so long as you're responsible about their care. Anything less then this, well you should worry.

 

PAR, I appreciate that...your right around the corner, I'm in Mt. Dora, I would love to give you a quick tour or what I'm working on (it's located just past Bay rd. on Old 441 in Tavares. Send me a note.