Cockpit Scupper Drainage (With Diagram)

[avd155]

Without going into too much detail, I’ve been planning how to deal with my cockpit scupper drain plan for over a month. I don't want to go into all the details, but the plan I had THOUGHT I decided on involves running each cockpit scupper "set" (forward and aft) to a below the water line 2” seacock. Problem is, a 2” Groco seacock goes for 4 TIMES the amount as a 1 ½” Groco seacock.. The cheapest is 2” seacock I’ve found sells for $279.99. Compared to the 1 ½” Groco seacock’s at $74.28, it's quite the price jump.

If you're really interested in the different permutations of this decision, I wrote a blog post with diagrams and pictures that describes my thought process. You can find it here: http://bristol27.com/blog/?p=146. It's not necessary to read the entire blog post, since for the purposes of this question, you really need to only view the following diagram which shows the "improved" drainage plan:



Since the 2" seacocks are so spendy, I am now considering running the aft cockpit drains to dedicated 1 ½” seacock’s below the cockpit. Not only will the cockpit drain more quickly, but I will save $411.42 ($205.71 per seacock). The question I have is how should the aft cockpit scuppers drain line be routed? As I see it, there are two options that stand out:

Option #1 – Position a 1 ½” seacock directly below the aft cockpit scupper so that there is a straight line from the aft scupper to the drain. This would be an above the water line seacock: draining below the overhang. I’m worried a line such as this might have some back flow into the line by following waves. Also, without measuring, I’d be willing to bet that the height of the seacock + the depth of the cockpit scupper fitting would be too tall to run proper drain lines.

Option #2 – Position a 1 ½” seacock about 12 inches forward of the position of the current cockpit scuppers. This means that each seacock has a 1 ½” seacock of dedicated drainage. Also this means that the thru hulls will be lower on the waterline (or just at it). The downside of this plan is that the drain lines will decrease access to my rudder post (since there isn't much room between the new, below the cockpit fuel tank and the rudder post).

There are probably other ideas or more to be said about option 1 or 2, which is why I’m posting here. Your thoughts?

[Rachel]

I don't mean to start out by challenging your plan (as I do just that....), but in order for me to think it through and give my thoughts, I'd like to go back to why you have decided to increase the cockpit drainage. Of course drainage is a good thing - I'm just interested in your specific reason(s).

What kind of an increase would you be getting by just going to 1-1/2" forward drains (i.e. what size are they now)?

Could you elaborate on how you plan to run the icebox drain into the cockpit drain line? That made me think "Hmmmm" when I saw it on the diagram.

Another note, if budget is a concern: If you are looking at the high-end Groco bronze seacocks, I don't want to discourage you because they are really nice ones and worth the money, in my opinion. However, the Apollo/Conbraco are also pretty nice, and they are very economical. When I researched them, in 2008, they were being made with all US bronze wetted components, and a chromed bronze ball. They are not as aesthetically pleasing as the top-end Grocos, and the handle is stainless and not cast (but easily replaceable); however they might be an option that would fit into your overall plan. Judging by the price you are probably not considering the "budget" Grocos, but just in case I will warn you away from them. In 2008 they were being made with foreign brass wetted components (after they recalled the stainless version). Of course things may have changed since 2008.

Rachel

PS: I like the diagram. Makes it very easy to see what you have in mind.

[tomwatt]

Hoping I'm not talking out of turn here, but in my B24, the aft cockpit drains (I think, but haven't checked so this is a guess) appear to dump into the aft well, and then drain out the bottom of that well. Is that ideal? I doubt it... but it would insulate you from having a wave push water into the cockpit.

[Case]

That aft drain behind the rudder post... that is really an odd thing to me.

Its not necessary at all. Normally, the cockpit floor slopes downward forward. So having a drain at the aft part of the cockpit makes no sense to me (unless the cockpit is totally flat or actually is sloped aft). Even more, its connected to the forward drains so if the cockpit gets pooped, having one more drain attached to one drain may actually slow down drainage...

About the seacocks, 1-1/2" is adequate, if you have two of them in the forward part of the cockpit. 1-1/2" is pretty much the standard size. I think its a waste of money to bother with 2" seacocks if the cockpit scuppers are 1-1/2". So, you're fine with the plan of using the 1-1/2" seacocks.

- Case

[avd155]

Thanks for the replies. From the replies, I realized I missed the obvious question, why not just go back to the original 1 1/2" forward scuppers and do away with the "after market" scuppers. It's actually probably the best idea, but before I go into why I also believe it to be the best idea, let me try to respond to your questions/comments:

I'm just interested in your specific reason(s).

Good question. My main reason was that I wanted to make sure I had a fast draining cockpit if I were ever to get pooped (as I plan to do a fair amount of offshore sailing). Since the boat's previous owner added the aft drains, I just assumed they were a necessary addition. My thinking now is that both Rachel and Case were right (I think) when they said the following...

What kind of an increase would you be getting by just going to 1-1/2" forward drains (i.e. what size are they now)?

About the seacocks, 1-1/2" is adequate, if you have two of them in the forward part of the cockpit. 1-1/2" is pretty much the standard size. I think its a waste of money to bother with 2" seacocks if the cockpit scuppers are 1-1/2". So, you're fine with the plan of using the 1-1/2" seacocks.

I want to measure the volume of my cockpit and find how quickly two, forward 1 1/2" scuppers would drain to 1 1/2" seacocks. If it's an acceptable speed, then I'll just stop all my head scratching and go with the original scupper set up. One thing is that I don't know of any official goal for the time it takes to drain a cockpit. Anyone out there know what an acceptable speed would be?

Could you elaborate on how you plan to run the icebox drain into the cockpit drain line?

Actually, that's an out dated diagram. I'm planning to move the icebox to a different location so just forget about that, sorry :) I will be posting new diagrams of my final interior plan as well as electrical and plumbing/tank drawings. So feel free to check my blog in the future you like the drawings.

Also thanks a lot Rachel for the information on the Apollo seacocks. I didn't know the difference between the metals even though I've also done done some research. I'll look into it more, but for now as long as I don't have to buy those 2" seacocks Groco is within my price range.

[Tim]

ABYC H-4 is the standard that covers cockpit drainage.

The details and calculations get complicated, so I've included the applicable formulae and charts from the two relevant pages of the ABYC standards.

If you really want to calculate the ABYC ideal for your boat, here's the info. But a pair of 1-1/2" drains is sufficient. If you're really worried about drainage and cockpit volume, then either spring for the 2" drains, or look for a way to reduce your effective cockpit volume in the first place. Something like James Baldwin's water jug storage locker seems a simple and proven means of effectively reducing cockpit volume while at the same time providing valuable stowage for something else, but there might be other ways that suit you too.

[jollyboat]

Tim,
Not to get too far off the subject, but in my own approach to the cockpit drains on both Jollyboat and Sepi, I think I set up a similar arrangement to what you have done in Glissando, where my gunnel drains and bench drains have been plumbed to dump into the cockpit first and then all drain out through the two 1-1/2" forward cockpit drains that are standard in "most" Tritons. I eliminated the under deck manifold style drain hose receptacle that were part of the cockpit drain standing water pipe assembly that was used on many Tritons and seem to always fail. (ice) The set up now is just to use a one piece, standing water pipe that all of the water drains through from the cockpit sole. Being that my sailing is bay and coastal I opted to not install sea cocks and just went with very high grade hose (white sanitation hose) and all stainless steel hose clamps (double clamped) to make up the standing water pipes. I am all for heading back to port for cheeseburgers and fries when the weather is such that the cockpit is getting pooped anyway so I am very happy with what I have described. It seems that this is an annual topic, yet I have never known of an Alberg design that foundered due the cockpit being pooped. I think maybe this upcoming summer I will try plugging my cockpit drains and filling the cockpit with water to see what happens. Sounds like a nice thing to do on a hot day to keep my feet cool.

[Rachel]

That would be an interesting experiment, I agree -- too see what a flooded cockpit does to the boat, and how long it takes to drain.

Although in a real-world, offshore situation, it would probably be a combination of problems that would get you. i.e. poor conditions, a pooping, then another wave, etc. So a quick-draining, low-volume cockpit is a good thing to shoot for if you (not you, but the original poster) will be taking your boat places where you might encounter those conditions.

That said, my gut feeling is that a well-installed pair of 1-1/2" drains and something (such as James Baldwin's cockpit locker) to reduce cockpit volume would be a good combination (and something that is reversible if/when one wants a roomy cockpit for coastal cruising).

On the W-32 we had a locker that reduced the cockpit volume by about half. That boat already has a smallish cockpit, but it has precious little deck/locker stowage, so it helped with that.

Rachel

[tpl]

> cockpit drain size...pooped

let us get this discussion in order. Cockpit drain size means
nothing unless other measures are taken. Once the cockpit well
fills question 1 is protection of your companionway.

many sailboats have cockpit wells draining directly forward
into the accomodation: no bridgedeck. Drain size doesn't matter.

even with a bridgedeck, I have seen it submerged in normal
sailing, by a wave breaking from astern--are your washboards
in place?

But if necessary, safer is to fit your bridgedeck with
non-removable risers, higher than your cockpit aft overdeck
drain point.

our drains are 2" bronze ball valves, straight down from 2"
cockpit scuppers, hose length about 2 feet. Additionally, P&S
the seats have individual drains to 1.5" bronze seacocks.

the water takes a *long* time going away, several minutes, I
guess. Big waves come along only every 3 or 4: that was fast
enough, and might be fast enough.