Question about freezing water in a pvc pipe

[JazzGuitarGimp]

Hi All,

I have a question for the physics majors out there. I have a thoery about a recently installed water tank and the pvc pipe that connects it to my house water system.

The tank, which sits in my yard, is about 8' in diameter, and about 7.5' tall, and holds 2,500 gallons of water. Connected to the output port at the bottom of the tank, I have a 1" pvc pipe. The pipe follows the ground (sitting on top of the ground, so exposed to the elements) for about 30', then enters an outbuilding where it terminates at the input of a jet pump, the output of which connects to a 40- gallon pressure tank through a check valve.

During the winter, the temperture here routinely gets down to the low- to mid-20's F, occasionally dipping into the teens, and on rare occasions, into single-digits. Because the tank is constructed from dark green plastic, the temperature in the tank is always considerably warmer than the outside air, and for purposes of this discussion, we will assume the water in the tank never freezes. The water in the 30' run of 1" pvc pipe, on the other hand, will in-fact freeze. I have installed a union at each end of the pipe, and a union in the middle of the pipe with the intention of draining it and breaking it down for storage during the winter. But after thinking about it, I have developed the following thiery which suggests draining and disconnecting the pipe is unnecessary:

I Know that the volume of water expands by about 9-10% when it freezes. Doing a rough calculation, 10% of the water in a 1" x 30' pipe is approximately 0.125 gallons. For all intents and purposes, the end of the pipe in the pressure tank shed is capped off. However, the end of the pipe at the 2,500-gallon tank has the ability to "push back" into the tank. Pushing 0.125 gallons of water into an 8' diameter tank would raise the water level in the tank by only 0.004". My thoery is as the water in the pipe freezes and expands, it will push back into the tank, rather than burst the pipe.

Am I all wet, or will the pipe be protected from damage?

Thanks,
Lou

[Reeltarded]

I wouldn't worry about a single night, but if there were a few days in a row that only got just above freezing and dipped closer to that teens number at night I think you might get some trouble.

The water tank is pump fed or manual fill? If there is even a drip of water flowing you are probably golden.. that is what we do here at least.

[M Fowler]

The water will freeze and push back in the available pipe space; however, from my experience that extra internal volume space available doesn't matter. The water freezes and expands finding weak spots usually at or near the valve or other joints and bursts even thought there was volume available for expansion.

Throw a tarp on that exposed 30 feet of pipe, or straw bales, earth mound, or heat tape, something! As long the water is flowing it will not freeze up.

Mark

[cbass]

Don't know much about no physics but my mind tells me that water freezing and thawing reapeabtly is gonna cause the glue on the fittings to fail or break at any unions.
Burry it afew inches

[cbass]

[quote="Reeltarded

The water tank is pump fed or manual fill? If there is even a drip of water flowing you are probably golden.. that is what we do here at least.[/quote]
Hell they can't leave water drippin out there that's probably a felony or something

[strelok]

I'm no expert when it comes to pluming, however I would be worried that some portion of the pipe might freeze solid and then any water down stream of where it froze might not be able to push back into the tank to relieve the pressure as it starts to freeze. I'm talking completely out of my ass though. I have no idea if this is even possible.

[Phil_S]

PVC gets brittle at low temperatures http://www.madisongroup.com/case-studies-pvc-pipe.html , making it even more likely to crack when the ice expands. I think the worst of it will be if somehow it affects the pipe joint at either end, making repairs challenging and possibly more expensive.

Look at digging a proper trench for that 30' pipe to keep it from freezing.

[stretch2011]

Try pex pipe out instead of pvc. It's around $1 per foot. It's way more flexible than pvc and can withstand below freezing temps.

Also if you have an air compressor near by with a long enough hose, or a small portable one, you can place a 1/4" male male air fitting at the output of the water tank. This will allow you to push all, or at least pretty much all, of the water out. That's how we remove the water out of injection molds. Takes all of about 30seconds.

[stretch2011]

Honestly tho to do it proper you'd dig a 3ft trench and blurry the line. But I know how much that sucks, I've done it plenty if times.

[ToneMerc]

Honestly tho to do it proper you'd dig a 3ft trench and blurry the line. But I know how much that sucks, I've done it plenty if times.

I agree especially if the soil is soft, get a sharpshooter and supply a good hour of muscle and be done with it. In northern CA I bet the frost line is relatively shallow and he could get away with it only being a foot deep.

TM

[stretch2011]

I don't know what a sharp shooter is but you can rent a ditch witch which looks like a chainsaw/dozer that cuts 4-6" wide trenches down 3ft.

[JazzGuitarGimp]

Thanks one and all.

The part of the system I've already described is an adjunct to an existing system that employs a shallow well with a 3/4 HP submersible pump as well as the pressure tank already described. All of the plumbing from the well head to the pressure tank shed, and from the pressure tank shed to the house is properly buried in the ground.

The well ran dry back in September, forcing me to expand the system by adding a 2,500-gallon storage tank, a 3/4 HP jet pump, several valves, nearly 100' of pipe, and a few toggle switches. So far, the only way I have added water to the 2,500-gallon tank is by having it delivered by a water tender truck. But I have also installed a pipe to the top, input port of the tank, and can switch a few valves in the shed to direct water from the well pump into the storage tank. The well just recovered a few weeks ago, allowing me to switch back over to the well for our water, leaving the storage tank unused for the remainder of the winter (with about 800-gallons in it). It was never my intention to use the big tank through the winter. However, it took longer than I anticipated for the well to start producing again, and I had to continue to use the big tank after the weather got cold enough to freeze the pipes. I have wrapped the outdoors-exposed portion of the pipe with insulation. But the whole point of laying the supply and fill pipes to the big tank on top of the ground, with unions at each end, was so that they could be drained and stored for the winter. Now that I have the supply pipe insulated, it will be a bit of work breaking it down for storage. So I am trying to justify my laziness with science.

Once the weather warms back up for the year, I will completely fill the big tank by running the well pump into it for a few minutes each day. From that point, it will sit unused until if / when the well runs dry in the coming summer. Hopefully one tank-full will get us through the dry-well patch, and I won't have to purchase more water.

This past summer was our first summer in this house. We were warned by locales familiar with the area that we were buying a house in an area that is known to run out of water each summer. However, I was here nearly every day during summer, 2014, working on the house, and I never saw any indication that I was running out of water. There was lots of drywall tools and paint cleanup going on.

This past summer was particularly bad though; we had a bad year for wild fires - one of which was only about a mile and a half from our house which raged for two months. The nearest source of water for the fire fighters, was the creek that runs along the back boundary of our property. They pulled their water tender trucks up on a bridge around the corner from our house, dropped their hoses in and helped themselves (I know that sounds like a complaint, but it isn't - I'm very happy they did such a great job getting the fires under control). But if that hadn't happened, I'm thinking it's possible we might not have run out of water. But now we are prepared for another water shortage.

I have thought about adding another small pump, maybe 1/10 HP, and adding it and a few more valves in the tank shed so that I can recirculate the water from the output port to the input port of the big tank. This pump could even be controlled by a thermostat so that it turns on when the temperature drops to about 28º, and then turns off when it gets back up to about 35º. This would keep the water in both pipes moving. But when I consider the added expense and work involved to do it, I am suddenly reminded that I am just being lazy about breaking down and storing the pipes the way I had intended.

Thanks again,
Lou

[stretch2011]

Hmmmm
Hhhhhhhmmmmmmmmm
Hhhhmmmmmmmmmmmmmmmmmmmmmm

I got it!

Fill your pipes with smoke.....and you won't have to worry about them freezing

Sorry couldn't resist.

Sounds like you have the right idea Lou, although finding the gumption can be like finding free money, just break down the pipes or dig a trench.

If you can use science to produce gumption you could make millions lol.