How to get water out of hot water supply network in house?

pyroboy

Hi all.

I have a house in the midwest (long cold winters). On the second floor I have two bathrooms, and the supply routes for each bathroom are different.

One bathroom's supply uses copper pipes and is routed via the interior, so no issues with freezing.

The other bathroom uses PEX, but unfortunately the line runs through an exterior garage wall (yeah i know **** right? wasn't disclosed nor caught in inspections but I traced the pex pipe and found it). Last winter, when temperatures dropped below 10°F, that PEX line completely froze. Between about 10–20°F, I think it partially freezes but doesn’t fully freeze so I can still get water just fine in that bathroom. However, I do notice during partial freezes, there's a small drip leak right under my vanity sink why the supply is. My theory as to what's happening is the partial freeze is causing expansion and increased pressure, which is causing that small drip leak, and/or some nut there isn't tightened enough... I've never seen this leak during warmer weather. This is a separate issue than the one I'm posting out.

Insulating the line properly isn’t easy right now, so my plan is to shut off the supply to that bathroom during very cold weather since I don't use that bathroom much. I’m trying to figure out the correct way to drain the hot and cold lines.

My main water shutoff is in the laundry room, and there's a sink there that I can drain from. My current idea is:

1. Shut off the main water line.
2. Open the laundry sink to drain the cold water supply
3. Close the valves that feed the PEX cold water supply line.
4. Turn the main water back on.

This should drain the cold line, but I’m not sure about the hot water line, since it’s supplied through the water heater. Would I have to drain the entire 50-gallon water heater just to empty that single hot-water run?

EBEBRATT-Ed

I assume the pex lines originate in a place where they don't freeze. I would shut the main water off and drain whatever you have to drain and install two valves on the pex so it will be easier to isolate them. Then refill everything except the pex. Downstream of the new valves install a tee in each line with drain valve on the tee's.

If the pex will drain by gravity to the new tee's isolate and drain open some faucets in the bath to let air in.

If it won't drain by gravity use an air compressor.

You don't have to get every drop out but enough so you don't have a plug of ice.

mattmia2

If you don't have a compressor large enough a shop vac also works.

pecmsg

small air compressor is all you need.
leave the water trickling and it won’t freeze.

pecmsg

if you can open the wall move the pipes closer to the interior side and insulate together with frost Tex heat tape.

pyroboy

Hi everyone. I don't have a lot of time to install anything unfortunately as I'm heading out on Thursday for a month and just want a quick temporary solution for now with the understanding I'll have to invest some $$$ in the future to address thie issue permanently.

Yes the pex lines originate in the basement utility room. It then goes to some crawl space between the basement, into a crawl space, up the garage wall. Right before the crawl space, there are shut off valves. But that only stops the flow from the hot water tank to that valve. The portion I'm concerned about is from the valve up to the 2nd floor bathroom. It was freezing somewhere in that portion some time last year (my guess is somewhere up that garage wall.

I don't have a compressor unfortunately.

I'm not sure how to disconnect the pex to let gravity do the work? How will a vacuum work?

mattmia2

Is there a waste cap on the valves to allow the pipes to drain?

Perr_y32

You don't need to drain the entire water heater for one line. You can turn off the hot water, then open the faucet in that bathroom and another one lower down (or near the heater) to drain just that branch. If you want to make sure no water remains, you can gently use compressed air to push it out.

pyroboy

https://forum.heatinghelp.com/discussion/comment/1876319#Comment_1876319

I don't believe so, but I will check in the morning

pyroboy

https://forum.heatinghelp.com/discussion/comment/1876324#Comment_1876324

I see. I just want to make sure I understand the flow here.

When you say turn off the hot water, you mean the shutoff valve I have for the hot water pex line right?

The thing is I don't think I have another faucet lower down — that one would presumably need to be between the shutoff valve and the upstairs bathroom?

DCContrarian

If there is no waste cap on the valve, cut the PEX and put in a tee and a drain valve. If you don't have the tools for PEX use Sharkbite. PEX is so easy to work with there's no point in fooling around, this is a five minute job.