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Last update 06/06/2012

Two Throwaway Tank Adapter

During my year of over-the-road truck driving I faced a dilemma - how to stay warm without idling the engine.  A big rig diesel engine uses about a gallon of fuel an hour while idling and that gets expensive, not to mention noisy.

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adapters adapted since 05/22/07

My solution is the Coleman Black Cat catalytic heater.  This is a charming little heater that produces no carbon monoxide and no fumes.  The newer version is made from plastic but it's still a good heater.  
The heater has only one problem.  A tank of fuel doesn't last long enough.  DOT regs require one to be off-duty for 10 hours every day and in the winter I tend to sleep most of that time.  A standard 1lb tank is good for maybe 8 hours max.  Ergo, I tend to wake up freezing.

One solution might be to carry a 5 or 20 lb propane tank along.  There are several problems with that idea.  One, DOT takes a dim view of propane tanks in the cab.  Two, size.  Three, getting it refilled.

One pound throwaway tanks are much handier.  They're easy to store, can be refilled if you don't mind some 'crat getting his panties in a wad and if one runs out he can buy them anywhere.  The problem remains, though, that one just isn't enough.

Enter the dual tank adapter.

This adapter is made from hardware store items.  A Mr Heater male disposable tank to 1/4NPT adapter, two female disposable to 1/4NPT adapters, a 1/4NPT Tee, two 1/4NPT ball valves, some 1/4NPT brass close nipples and two 1/4NPT brass street elbows plus some epoxy.    
Here's the adapter attached to the heater.  the male fitting, the one the heater attaches to, must be fixed at an angle so the heater will stand on its legs while keeping the cylinders more or less upright. 

The male fitting must also be radially oriented properly so that when the heater is tight against it, the legs point down.  I achieved this by coating the NPT pipe threads with epoxy, screwing the heater on, tightening the NPT joint until snug and then rotating the heater until the legs pointed down.  I allowed the epoxy to cure and everything was locked into place.

A rotary joint is called for here but I didn't have one handy.  So far this alignment has worked well.

I used epoxy on all the threads because the whole assembly needs to be rigid.

The first photo shows the adapter attached to two tanks and a hose.  This is a standard Coleman male to female disposable cylinder hose that lets one locate the cylinder away from the appliance.  When there's room, such as in my motorhome, I use this hose and store the tanks out of the way.


When I go to bed I start out with one full tank and one from the previous night.  The previous night's tank is the combination of the two previous night's tanks combined into one using my Tank Drainer.  I connect the two tanks together when I start out and when it's time to sleep, the top tank is drained.

The two tanks tend to equalize levels over the night so in the morning, both are at about the same level.

If I stop during the day for a break, meal or nap, I'll run only one tank (one valve closed).  That will more fully drain that tank so it won't take so long for the Tank Drainer to work.

Frost-Up Prevention

This adapter has another use - supplying appliances such as mult-burner cook stoves, radiant heaters and so on that draw propane so rapidly that one tank will frost up.  Once frost forms it insulates the tank and the temperature and pressure drop until the appliance may go out.  This is particularly troublesome for unattended appliances, as a small amount of propane will still issue forth and will at minimum, stink, and at maximum could cause a fire.

So far I've not run into any appliance designed for throwaway cylinders that uses propane fast enough to frost up two cylinders.