Can Flushing Your Toilet Keep the Water Main from Breaking?

Factual Questions
1

I live in Detroit. And this post-December period especially, we seem to be having alot of water main breaks (or so they tell us on the local news). Water main breaks can be a problem if you’re near them. They may have to shut off your water, and your basement runs a risk of flooding. I’ve noticed it seems to only happen on the coldest nights, which makes sense. Late night/early morning is the coldest time of day wherever you are. And plus, I think, it is also the time when people use water the least, thus letting the water remain dormant in the pipes, and giving them the opportunity to freeze.

Now they tell you the best way to avoid pipes freezing in your home is to run a little water. Just a trickle should be enough, they tell us (on the news, etc.). But what I wonder is, would this logic apply to flushing toilets? Because it may sound silly. But I usu. stay up late anyways. And on the coldest nights I flush the toilet every couple of hours. And so far it seems to be working. We haven’t had any problems in our neighborhood.

Does anyone know if this would work? Or does anyone at least have any thoughts on the matter? As I’ve said, I want to do whatever it takes to avoid a water main break in our neighborhood.

:slight_smile:

2

Your water mains do not break at night because they freeze; they break at night because that is when the pressure inside them is greatest because usage in at its lowest. So yes, your flushing solution is (insignificantly) helpful, but not for the reasons you state.

3

I’ve never heard this before. My experience with broken pipes has always been in the winter.

4

Yes, I’ve only had burst water pipes (mains or local) in the cold of winter. As I understand it, water freezes and expands, breaking the pipe.

5

I think the cold making the metal pipe brittle has more to do with it that ice.

6

.
That turns out not to be the case. Or at least not the major cause.

Have you ever put a bottle or can of soda or beer in the freezer and forgotten about it? The expansion of that ice as it freezes creates incredible pressure. (This spoken as a man who, just a few weeks ago, was up at 4AM repairing burst pipes in the the balmy -15F of my basement, where someone who will remain nameless left the outer door unlatched with 40 knot winds.)

Another piece of evidence is that the water stops flowing through the pipe before it busts (because it’s plugged up with ice).

7

Freezing weather makes outdoor pipes break not because the water inside them is freezing but because the ground around them is freezing. Frost heave is causing the pipes to flex. Different types of soil, depth, etc., cause different amounts of flexing. Even though the pipes should be buried deeper than the frost line, changing pressures on freezing soil above them can still cause flexing. Over time, objects below the frost line can be worked up towards the surface.

Flushing the toliet a couple times a night will have no significant impact on this.

8

There seems to be a lot of mis-understanding about this.
When water freezes it expands.
Solids don’t compress very well.
Something is going to give, most likely the pipe.
Frozen pipes are likely to split, not break off cleanly.
During a cold spell it is a very good idea to run a slight trickle of water.

9

Herman & Bill and hammerbach, the information in your posts may be all well and true for household plumbing, but it does not apply to water mains because – unless they were installed by idiots – they lie under the frost line. The frost line, as its name implies, is a soil depth (that varies by region, btw) below which the temperature does not reach the freezing mark. The soil does not freeze below the frost line, nor do water pipes.

ftg’s comment about frost heave may, on the other hand, have some validity. It is a potent natural force, but I’m remain dubious about its effect on an object so massive and (presumably) deep as a water main.

10

When I was in the Military stationed in Alaska, we always let our water run at a trickle all day and all night. Sure, this increased the cost of water for the base, but the cost was much less than a big break in the water main. Never were we told to flush the toilets occasionally.

11

Depends on what we are really talking about.

A water ‘main’ is incoming water. A slow trickle can help keep these from freezing.

The big question is… Is it just your house, or the neighboors as well.

A slow trickle can slowly fill up your waste pipes and slowly freeze. Leaving you with incoming water but no drain.

Water ‘main’ break up is (as other posters have said) caused by freezing and heaving of the ground. The same thing can happen to waste water lines.

If your incoming water supply to your house is freezing up, isolate it. Find out if any room still has incoming water. Turn a little bit of hot water on in the room that has running water, and turn up the heat in the rest of the house.

All houses have one incoming pipe. It usually runs right to the water heater, where it splits off. From there, they run pretty close to each other to the other plumbing. If you experience a freeze in one part of the house, a little hot water run through other pipes can help warm up other pipes and thaw them.

12

I think the crux of the issue is that the OP may not be stating what a “water main” is correctly.

I assumed the OP wasn’t talking about a true water main, buried outside in the street and serving the whole block. Those things obviously are not affected by just one house doing a couple of flushes.

My “second guess” was that the OP was referring to the branch line from the house to the main.

But it could actually be about the pipe once inside the house. (Water in basement and all.)

The OP needs to clear this up.

I lived in a frozen place for 7 winters and the most common kind of (true) water main bursts in winter came about this way:
There’s a slow leak in the pipe. It floods the neighboring soil, washing some away. This type of condition can freeze lower down than just regular soil. It freezes (mostly), making the problem worse but things are held in place by the ice. A thaw comes, the frozen soil washes away, etc. Pipe breaks. So it was more a phenomenon of a thaw after a freeze.

Again, stuff that was once below the frost line can sometimes work it’s way up. Those rocks in New England farm fences didn’t all come from above the frost line.

13

Yes, I’m aware of the frost line. But this January has been unusually cold, and more importantly for those of us here in Maine, snowless. 1/4" of measurable snow, which would normally insulate the ground this time of year. So pipes which would normally be below the frostline are now freezing up. (Note that they stop running first, THEN burst).

14

ftg is the closest so far, but further down the thread it got muddled. So Here is a roundup of most of the possibilities…

Water Main - The water main break that the OP mentions that gets noticed on the news in Detroit is a broken city water main. These are the large diameter (typically 8" in a residential area but up to 48" for large transmission lines) city water main that is typically buried under the street. These pipes were made out of cast iron before the late 60’s, ductile iron from the 60’s on, and now can also be PVC. Some large transmission lines were actually made from asbestos cement. They are almost all below the frost line. These pipes almost never freeze.

In Detroit there are likely miles of 70 year old cast iron pipe still in use. Cast iron resists corrosion well underground in good soil, but is very brittle. One failure mode is radial cracking, occasionally but not usually completely severing the pipe, from exactly the reasons ftg mentions. This is the most common winter break. Internal pipe pressure is not a factor in this break.

Another common mode of failure is localized external corrosion from a soil hot spot (often something like a place where old cinders were dumped). This causes pitting that gets deeper and deeper and eventually eats all the way through. Pressure does make a difference here, but the pressure change your toilet can inflict on an 8" line is unmeasurable. This type of break can happen any time of year, but is slightly more common at times of soil motion adding just a little more stress on the pipe (ie, when there is freezing or thawing going on.)

Either of these breaks can pump thousands of gallons of water rapidly to the surface and flood basements for a block. They are capable of hollowing out all the dirt under a road and causing a giant sinkhole. They make the news.

OK, then on to the water line coming into your house… A 3/4" to 1-1/4" line is tapped into the side of the city water main and run through your yard up to your basement. This is either galvanized steel, copper, or PVC. It is installed by the plumber who worked on your house. It is supposed to be below the frost line but cheap contractors have been known to bury them a little shy in the past. Steel and PVC can break from soil pressure, copper not so often. Steel and copper can both be hit with corrosion. These types of leaks will cause you personally great distress and expense, but likely won’t affect your neighbors and won’t make the news. Water pressure will make a neglible difference.

Lastly, if the line to your house is buried too shallow it CAN freeze, and leaving water running will prevent this. Constant running from a faucet is much more useful than flushing the toilet. But if the line to your house freezes it will not always flood your yard. It will freeze the water in the pipe, break the pipe, and then… it might sit there until it thaws. The ice occasionally forms a good plug.

So there you have it from someone who wishes he played a civil engineer on TV rather than actually being one.

(And as hammerbach notes, a snowless unusually cold winter can drive frost deeper than usual and bite the folks who have water lines that were just barely deep enough for a normal winter. Hey! Preview IS my friend!)

15

Thanks for that much more informative than mine post! Out of sheer nosiness, where do you practice? Seen many of these? I have often though about going into your field, at least when mine is slack…