Connect COLD & HOT, what happens?

[SeeMyProfile]

Take this situation: hot and cold water silcocks are located in a garage. The hot is allowed to run so the water is hot at the outlet.

This a standard residential installation. The heat is forced air natural gas and has no connection to the plumbing.There are no in-line pumps of any kind, nor are there any one way valves or vacuum breakers. The piping is copper and the residence is 25 years old.

A standard garden hose is connected, one end to each silcock. Both valves on the silcocks are opened simultaneously.

Is there any flow between the two silcocks? If so, which way is the water flowing . . . hot to cold, or cold to hot and why?

 

[JohnjH2o1]

As long as nothing else is opened in the water system there will be no flow.

John

 

[Sponsor]

 

[hj]

hose

Whether the hot system is hot or not is immaterial. There will only be flow if there is a pressure imbalance between the hot and cold systems, and the flow will be from the one with higher pressure to the one with less pressure, regardless of the temperatures. Now, if conditions were right, and the hose connection were made so it could happen, there could be convection currents in the hose which would transfer heat from the hot side to the cold, but that would require a precise method of interconnection, and it would not be a "flow", since no water is actually transferred.

 

[Jimbo]

In my experience, water will migrate from the cold side back into the hot pipe. The physics involves might be that the pressure on the hot side is slightly less, due to more pipe and fittings, including tank fittings, OR it could be convection of all the heat out of the hot side.

Whatever the real cause, this is the reason that any shower head which has a "pause" feature, has a slight built-in drip. The drip maintains more or less the temperature you were using. If you put a hard stop on the shower arm or shower head, when you turn it back on, it is COLD!

 

[hj]

cold to hot

The reason the cold will normally migrate from the cold to the hot, is that when water is being used elsewhere, the hot has a longer path, i.e., from the common cold water supply, to and through the water heater, and then to the faucet with the cross connection. This longer path results in a greater pressure drop, so the cold water zips across to make up the difference. The cold water seldom has a higher pressure drop than the hot, unless it is a galvanized system with corroded pipes.

 

[SeeMyProfile]

There is a PRACTICAL application behind this thread.

I live in a cold climate . . . Michigan. I use a wet saw during the winter to create craft materials. My wet saw is in the garage and the water gets so cold that I can hardly stand to use the wet saw for more than a couple of minutes at a time because my bare hands are exposed to the water. And, if the water freezes, it's destructive to the water pump.

I'm trying to figure out a system to use the hot and cold water in the garage to keep the water at a bareable temperature during winter.

The Wet saw pan contains about 5 gallons of water. I can't just dripple hot water into the pan because it would overrun the pan. There isn't a drain in the garage floor and directing the overflow outside wouldn't work either. Directing the overflow into a bucket is impractical since I'd have to always be watching the bucket and then go outside and empty the bucket constantly.

I've thought about using the system that uses a pump to keep heated water at remote bathrooms but don't like the material cost or the installation hassle. And I don't need this in my condo.

I've thought about an emersion heater (like used in coffee cups to heat the water) but consider it too dangerous; putting an electric heater under the metal pan (potential problem with splash water and heater); using one of those "embedded under tile electric heaters"(cost of materials, safe with water?); and even using a very small boiler system using a small LP tank (possible Co poisoning in an enclosed space, cost, design?); fish tank heater (too wimpy to work), etc.

I'm also thinking of a closed loop system that heats water inside a soft copper helix (or other copper configuration like in rows using 90 degree fittings) in the water (or under the water pan) and returning to the "system".

I should say also that the water heater and the piping to the garage are open and very close to each other . . . maybe 10 feet apart. It would be possible to add whatever copper piping is needed to accomplish my goal.

Can you think of a way to use the heat from the hot water heater to keep my wet saw water warm and yet do it cheaply enough that it makes economic sense? I'm out of ideas. . . .

 

[Jadnashua]

What about a fish tank heater?

 

[Nukeman]

What about a fish tank heater?

He mentioned that in the post. Anyway, this is what I was thinking too. You should be about to get a couple in the 150-300W range and toss in there. The nice thing is they have a built in t-stat to help regulate temperature. I think this would be a simple/cheap solution for what you are wanting to do. You may not have hot water, but it will at least be lukewarm.

 

[hj]

heat

NO matter what you do with the hot water pipe, it is not going to help the tile saw, because you fill it and then circulate the water. Even if you fill it with hot water, it will cool, and fairly quickly because you would be circulating it and also spraying it on the blade. The ONLY way to keep the water warm would be with some type of immersion heater. A UL rated water heater for a fish pond or watering tank would work, if you find a small one.

 

[weaver]

Another Immersion Heater

There are sturdy ones made to keep bird baths from freezing...

 

[Frenchie]

Electric baseboard - heat the garage.

 

[Kreemoweet]

Small immersion type heaters are widely used by pro tile mechanics. Any tile/stone
worker's supply house would probably have them.

 

[Jadnashua]

The garage power should be on gfi protected circuits, but is it isn't, it would be a good idea to fix that, especially if you are going to play with a heater and your hands may be wet while standing on a wet floor!

 

[hj]

heater

The heater will be IN the water, so it wouldn't make much difference what he was standing on.

 

[Export!]

5Gal is a pretty big sump. How much tile crud builds up in there? In my experience with much smaller saws it's a lot. I wonder if it would cake on a fish heater and cause it to cycle off earlier than it should?

That being said, the fish heater still gets my vote.

I've built home breweries with counterflow wort chillers and know the same principles would work to heat a given vessel of water but that would probably not satisfy the cheap and easy requirements. I dare say it would border Rube Goldberg territory.

 

[Export!]

How about a tiny electric hot water heater in a closed loop with mag pump to recirculate through a coiled copper mainifold inside the sump. Use a ball valve on the output of the mag pump to slow the flow down to the point where the return of the manifold just reaches the same temp as the water bath.

 

[Jadnashua]

The worst thing to do is have a path for electricity through your body...hands in a wet saw and standing in wet means it might end up traveling through your body...

Saw a guy get zapped with high voltage one time...traveled through his arm, out his elbow, and burned additional holes in his boots with charred areas around the hobnails. He was lucky to be alive.

 

[Frenchie]

Okay - in all seriousness - MK makes a water heater for wet saws. It's about 50 bucks.

http://www.contractorsdirect.com/Tile-Tools/Other-Tilling-Tools/Water-Heater

http://www.amazon.com/Electra-5-1-2-Water-Heater/dp/B000R01TPS


I still say you should heat the garage.