Due to a furnace issue, I have no heat in my home. The temperature now is about 40 and will go down to around 15 overnight. There's nothing that can be done about that until the morning. It's also not supposed to get any warmer than 20 tomorrow. I really don't want a frozen pipe issue either. Should I shut off the main to my house? Or leave the water running slowly? If I shut off the main, I don't have a way to flush the pipes completely.

Best recommendation?

I don't have a way to flush the pipes completely.
Is the main stop to the house a stop and waste valve?

You can flush the pipes. Turn off the main at the house or the street. Open all outside hose bibs and all cold water faucets in the house, should drain all CW. Now, open all hot water faucets and drain about 5 gallons of hot water from the HW heater. Should drain all HW. Leave the faucets open.

Hmmmm...

Really a tough call here. I have seen too many burst pipes as a result of improper draining...usually the result of improper plumbing design that traps water in places that are almost ALWAYS in the most ridiculous places we can image (Bit*ch to repair)!! As you said, Iceandrews, "I don't have a way to flush the pipes completely".

Here, I would suggest letting all the faucets/valves in the home run water at a dribble...both hot and cold. This will protect the water pipes, the water heater and all fixtures that have PTRAPS (that almost always freeze/break in inconvenient places), as well as the water meter.

I would probably turn the water heater gas valve down to vacation or pilot setting (or if electric water heater I'd shut the breaker off)...no need for hot water right now.

Now, what some might say is overkill, so you decide if you want to do this if this is really only for one night:

Next, toilets should be made to dribble by lifting the flapper and reducing water flow to a dribble through the cold water shut off of the toilet(s) so that water trickles into the toilet bowl.

The washing machine: Connect the hot water hose to the cold water supply (or vice-versa) and open the valve(s) at the washing machine....hope for cross circulation. I'd also add antifreeze to the washing machine PTRAP.

The dishwasher: Because the DW is usually connected to the hot water feeding the kitchen faucet you can only hope the hose feeding the DW won't burst overnight.

Outside faucets: Hopefully, just shut the water off to these and try to drain these units and their pipes if properly pitched.

Condensation pump from furnace: should survive overnight.

I'm sure I'm forgetting some things, but you get the idea!!

If more than a day or so, you would really need to WINTERIZE the home and that requires flushing the pipes (using compressor) and "environmentally safe" antifreeze and a bit more work, so post back if this is going to be longer term, OK?

That's my thoughts guys!

Mark