Ice box p-trap

[Amgine]

We're recently back from a longish summer cruise where I did some experiments with the ice box. One of the things we tried was using dry ice, which was a huge success. 50# block lasted a week, and for the first 3 days everything in the icebox was frozen solid - a bit of a problem actually, but not a bad one in the long run. No water running into the bilge as it melted, no "fridge smell" in the bilge either. The one 'downside' is fresh fruit and veggies stored in the icebox became mildly carbonated - not bad with the cherries, but not so good with the sugar snap peas.

However, it became really clear really quickly that the cold CO2 was pouring down the icebox drain into the bilge. It got me thinking about an argument Donald Street made for having a sink-style p-trap in the drain under the ice box to prevent the cold air from just running out the bottom. Has anyone ever installed a p-trap, and does it help your ice last longer?

[Steve Laume]

We keep a closed cell foam plug in the drain hole.

To keep the ice water contained, we start with frozen containers from home. Once they melt we use the water for coffee or drinking.

We then try to get block ice after that. Any ice we get during a cruise goes into a dry bag before it goes into the ice box. When it melts it is contained in the bag and we dump it overboard before adding fresh ice.

Any fish or meat goes into a sealable plastic container before entering the ice box.

Although this is not a perfect system it is better than having all that water sloshing around with half melted cheese, veggies and meat juices.

The dry ice sounds like a great idea. Maybe a combination would be the best solution.

I did a surf fishing trip to Hatteras when I was very much younger with a bunch of guys. We only had one cooler into which went all of our food, beer and bait. Everything had the distinct aroma of the mullet water it sloshed around in.

The beer still tasted great and I would imagine we smelled a bit like mullet before the end of the trip too.

We did have ourselves some fun, Steve.

[The Patriot]

... Has anyone ever installed a p-trap, and does it help your ice last longer?

I fitted a trap in the icebox drain hose in my CD28 many years ago while I was living on the boat and wandering among the islands. I cannot provide convincing statistics or data, but my impression is that not allowing the cold air to sink into the bilge (where the hose drains) helped the block ice last a bit longer. In fact it seemed like a lot longer, but I cannot support this with hard data. It also can help when some "nasties" escape their containers in the icebox and try to head for the bilges.

[Michael Heintz]

One of the best improvements I ever put on board Macht Nichts was an Isotherm refer unit. Sold by Great Waters. You can check out the specifics on line but let me tell you it's great. I did beef up the insulation of the box and put a plexi divider so that the area closet to the cold plate keeps food well frozen, the balance of the box is perfect for the rest of the fresh veggies and other things. If you cruise a lot this is a most important upgrade. And I do not have to chase ice!!!!!! (BTW I do keep a small bag of cubes for cocktails and I never lack a cold beverage)

The second best addition was a windless!!!

[Neil Gordon]

Has anyone ever installed a p-trap, and does it help your ice last longer?

When I (rarely) load up with ice, I simply put a Rubbermaid sink thingie over the ice box drain. Removing it does require that I work around the beer bottles, etc., and plunge my hand into freezing cold water but it otherwise works well.

[Joe Myerson]

Using a dry bag for the ice sounds like a great idea.

This year I slipped the end of the drain hose into an empty gallon milk jug. It has made a big difference keeping the bilge dry and clean.

--Joe

[Amgine]

I guess the point of my question got lost in translation.

The p-trap is like the one on the sink in your house, where the pipe does a little s-on-its-side shape. The reason why it's there in your house is it will trap a bit of water in the pipe, which blocks the methane (stinky gas) rising up from the sewer pipe from getting into your house.

Don Street suggested that cooled air drains out of the ice box, 'taking the cold with it,' and that a p-trap would slow down how fast ice melts. I think this would be even more true when using dry ice, which 'evaporates' to cold air. If the ice box drain had a p-trap in it I would hope the CO2 would stay in the box, and keeps everything cooler longer.

Just wondering if anyone (Thanks KerryDeare!) has tried this, and if so what were the results?

[Joe Myerson]

Sorry Amgine,

You did raise a good question.

As a follow-up: How does one install a P-trap into the drain of the CD's built-in ice box.

--Joe

[Amgine]

<grin> Haven't gotten to that stage of the plans yet. My guess is it would be a real pain in the tuckus.

I would think it would have to be a semi-rigid, non-collapsible hose, probably something of the kind used for heads, forced into shape using hose clamps. It has to be hose, to fit onto the existing barbed fitting and - for my purposes - so it won't fail if the trapped water freezes due to the dry ice.

Having dug around under the ice box on my CD25D (#176), there's almost no room to work with. (also, the bottom of my box appears to be un-insulated.) I think this is going to be the hardest part of the job; attaching the new plumbing.

[Joe Myerson]

the bottom of my box appears to be un-insulated

You're right there; the ice box is NOT insulated.

Veering off-topic again here:

However, the uninsulated box seems to hold cold fairly well ONCE IT GETS COLD.

On Creme Brulee's last cruise--to Narragansett Bay for the Northeast Fleet rendezvous--we got the ice box cold by putting, one after the other, three frozen gallon jugs of drinking water. We kept the jugs in a soft cooler that will keep ice for a long time if not opened. We also put a folded-up "space blanket" at the top of the ice box before closing it.

The first jug lasted less than a day; the second lasted longer. By the time the third had melted, we were at Dutch Harbor, where we purchased a block of ice.

The block ice lasted for three days.

But that still doesn't address the PITA of trying to add a P-trap to the ice box.

--Joe

[Steve Laume]

Okay, the P trap is a very simple arrangement on the boat. In fact I believe the original drain on Raven was set up to work like that. Unlike a home system where you could syphon out the trap if not vented properly the boat is simple.

All you really need is a higher loop in the drain hose. Leave the bottom of the ice box, loop up slightly and then send the drain onto wherever you want the nastieness to go. Water will sit in the lower looped section of the hose and form a trap. If you flushed it out quickly it could siphon out the loop but then all you would need to do is refill it slowly.

Please do understand that whatever water sits in any trap is not going to be real pleasant stuff. That is why we try to keep a dry box. You can flush out the loop at any time to clear it.

Our box did not appear to be insulated but in fact it did have about an inch of foam between the inner liner and outer box.

I drilled a grid of 1 inch holes completely around our box last summer. Then I got a mess of those low expantion foam cans. Fill slowly and expect to go back a second time rather than have a huge amount of erupting foam and possibly the deformation of your liner. After I was done foaming I epoxied all the hole sawed plugs back in and spread a couple of more coats of thicken epoxy over them. Sand fair and paint. The bottom is more important than the top but a good seal around the cover is essential too. The box stays much colder now.

Extra insulation would seem like a good first step no matter how else you treat your cooling needs. You will save either ice or electricity.

The foaming project was not that difficult, Steve.

[Troy Scott]

Many Cape Dory iceboxes are made as a box within a box, where the dead air space between the two shells provides the insulation. I filled the dead air space with expanding foam which I think does a better job.

For the drain, I installed one with a plug, similar to a bathtub plug. This will certainly stop the cold air from escaping. I decided I did NOT want a trap, because the water in traps often gets really foul.

In the CD36 the icebox and the shower drain into a small, separate bilge. An automatic pump will keep this small bilge emptied before it has a chance to mix with the larger bilge.

[M. R. Bober]

Former Chesapeake Fleet Captain Neil Kozlowski installed a shutoff valve in the drain line from the reefer. When it was desired, he would close the valve and keep the icy water in the bottom of the reefer. When the water got too high or at the end of a cruise, he could easily drain the box. No cold hands and canned beverages awash in ice water; win win.

A "P-trap" by design will normally have liquid (to prevent "sewer gas" from backing up into a house. If you spill something nasty, it may be with you for quite a while.

Mitchell Bober
Sunny Lancaster (where cold drinks are always available in winter,) VA

[Jeff G]

I "sort of" built one for my 25D. First, there is next to no room between the bottom of the drain and the hull. I used some heat and some metal to form a suitable shape in a reinforced plastic hose (somewhere between 90 and 45 degrees). That was the hard part. The trap was easy. I used one coil in the hose line to form the trap. Make the coil loop generous enough to allow water to be trapped at the bottom of the loop. Zip tie the hose in place and you're set. Originally I just wanted to stop water from entering the bilge by diverting it into a soda bottle. I just happened to have too much line so I coiled it. Turns out it made a decent trap

[M. R. Bober]

Keep in mind that at temperatures above -109F dry ice (CO2) goes through a phase change and becomes gaseous. Be sure to provide adequate ventilation.

Mitchell Bober
Sunny Lancaster (where it is normally well above -109F,)VA