Older, bigger plants have roots that go deeper and have access to more water. You can see the same effect in gardens, where new plants wilt sooner than established plants (and the care instructions advise frequent watering for the first couple of weeks).

Austin is close to 50% leakage. Now up to 110gal/day per connection in 2024.

https://www.kxan.com/investigations/city-of-austin-pipes-lea...

That’s really high. There’s either a big problem in your city, or they are making generous estimates to justify asking for more capital. 10-15% is more typical.

In my region, the street trees are usually getting sewer water. Residential service in older houses are usually clay pipes with lead solder that the tree infiltrates. It’s not a problem until the clay pops and roots clog it.

It varies a lot by region and jurisdiction. One of the cities near me made the mistake of using riveted pipe from rolled steel to save money 75 years ago, and regularly has catastrophic main breaks as the rivets aren’t as robust as a regular pipe.

With a Botany of Desire angle:

Trees have led the humans to channel water and irrigate them so they survive even in dry and isolated soil, and provide shade for urban areas in exchange.

  >Since street trees can’t get much of this from rainwater, which falls on concrete and drains into the city’s sewers, Poirier says the most likely explanation is ...

  I feel like this is burying the lede. What can be done to reduce leakage?

This is hardly a pipe dream. Village Homes demonstrated the concept[0] over five decades ago.

[0] https://www.youtube.com/watch?v=zZ7RmsJOlgc&t=980s

> What can be done to reduce leakage?

Do we really want that? Thousands of people are being killed each year by heat strokes. Keeping those trees alive by its environmental services is much more valuable in terms of lives and also energy saved. Maples have soft big leaves but also reduce the asphalt temperature by 5-10 degrees. If required just plant a tree species that can live with less water.

While there are some interior pipe lining solutions, they are just kind of a short term bandaid that will cost more in the long run and has its own complications, the only real answer is to bury brand new pipe. And that can get expensive if a lot of stuff has been built on top and around it which is why most municipalities just live with even major leaks and kick the can down the road until it breaches the surface and starts flooding areas. It is probably cheaper to replace them sooner rather than later in the long run, but no politician cares about how well a city's finances will be decades after they are gone.

Hopefully the lede, lead would be an even bigger concern.

Why should anything be done to reduce leakage? They take water out of the St Lawrence and, as much isn't diverted by trees, it goes back in (cleaner then when it came out.)

Yeah let's wilt all those pesky maple trees in Canada

I use to live on a property in a development. On my property were a pair of big willows. The trees were large and healthy, well over 50' tall. That was strange, because the region is high desert with little water, and I made no effort to irrigate them.

One morning in spring, after I'd been living there about 15 years, the neighborhood streets flooded. There were geysers of water shooting up from manholes. Turns out, the willows had been planted over an irrigation ditch[1]. The willows had driven their tap roots into the pipeline and plugged it about 10' underground. When the water authority opened gates miles upstream, the water pressure blew water up the manholes into the streets and a few yards.

Farmers are very motivated to get their water. They, and the ditch company, rapidly cleared the plug and removed the trees.

Before this happened I had no idea the irrigation system ran through the property. I knew about an easement, but I thought it was for sewage, because the developer used an iron manhole cover from the local municipal waste management operation when they covered the irrigation ditch: it literally had "Sewer" cast into the iron.

[1] Formerly an actual ditch, later made into a pipeline and covered over, but still technically a "ditch" for purposes of water management.

Or at least, constant supply for the several hours it will take to call a rooter company and clear the drain line. Ironically, the tree would have better results if it only partly blocked the drain. I wonder if trees might ever evolve to strike that kind of balance, or if there's not enough selection pressure for that to happen.

We had a lemon tree that did this. The irrigation line connector was probably not 100% sealed and the roots grew to it slowly broke it. It enabled the lemon tree to gets lots of water and grow. Meanwhile the trees further down the irrigation line suffered.

Some genius planted a curly willow right in the middle of my house’s septic drain field. That tree cost me $20,000.

Tetraethyllead production was very centralized by Ethyl corp/DuPont and required a higher purity lead ore so their isotope ratios are very well known based on the deposits that they mined. More locally sourced lead used for construction will have different isotope ratios.

When you need a lot of lead (enough to build plumbing for a neighborhood), you probably want to source it locally. When "1 part TEL to 1300 parts gasoline by weight is sufficient to suppress detonation",[1] you can source the lead from just about anywhere and ship it with the fuel.

1: https://en.m.wikipedia.org/wiki/Tetraethyllead

We didn't put elemental lead in gasoline, it was a very different molecule with a single lead atom. Given how dense lead is, you want to source it from as physically close as you can. A foundry making pipes in a city with a lead mine nearby will obviously use the local lead.

For gasoline, all production had to be centralized in a few refineries. The lead would have been shipped in, and would have been largely the same quality and age, likely coming from the same mine, or geographically close mines. Plus the absolute quantity of lead added to gasoline is relatively small. In the 60 years the US used TEL, we processed about 8 million tons of lead. Averaged out, it's 133 thousand tons a year. It would only take a few mines to provide that much. Probably not more than five or ten, but I can't immediately find good data on this.

One would expect that the lead used in gasoline is pretty homogeneous across time, and that intensive lead use (as in casting into solid metal object like pipes) would use the nearest available source, and use that source for as long as possible.

The radioactive lead isotopes come from decay of uranium and thorium, so lead from different mines will have different isotope ratios depending on how much U and Th happened to be in that ore.

Not all leaded gasoline was the same either:

> 206Pb/207Pb ratios commonly found in Pb ores throughout the world range between 16.0–18.5 and 1.19–1.25, respectively (Hansmann and Köppel, 2000). Exception to this rule is the commonly used Pb ore from the Broken Hill deposit, Australia, which is characterised by extremely low 206Pb/207Pb ratios (1.03–1.10). On the other hand, Pb originating from the Mississippi Valley ore deposit, USA, exhibits significantly more radiogenic Pb isotopic composition (206Pb/204Pb N20.0; 206Pb/207Pb= 1.31–1.35) (Doe and Delevaux, 1972). American leaded gasoline reflected therefore significantly higher 206Pb/207Pb ratios compared to European gasoline (Fig. 1). The introduction of the European leaded gasoline around 1945 resulted in a steep decrease of the 206Pb/207Pb ratio of atmospheric Pb (Weiss et al., 1999; data from peat deposits). The isotopic composition of leaded gasoline was to some extent dependent on economical factors, such as the availability and price of Pb ores and has evolved due to the different Pb ores used. For example, Pb used for French leaded gasoline originated from Australian, Moroccan and Swedish ores and the contribution of the separate ores changed during time (Véron et al., 1999). It is therefore indispensable to gather data concerning the origin of gasoline used in studied regions.

[from https://sci-hub.ru/https://doi.org/10.1016/j.envint.2007.10....]

lead from pipes was mined localy, but the lead in parks soil is from airborn pollution and so the isotope signature will be quite different

Heh. Yesterday, we had a plumber over who told us we have to rebore our sewage pipes because roots got in. It is an old house with cast iron pipes and they still got in.

Decades? Try millennia.

there is a new to me datum in that trees along residential streets are experiencing less water stress than trees in parks, due to city water leakage that was demonstrated by doing core samples on the trees to show how lead isotopes differed in the two populations of trees. it highlights a growing concern with water in general and how carefull water monitering and management is becoming, and how what was primarily interesting to civil engineering types, has a wider audience

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That double wall thing is a red herring. The water system already protects against intrusion because the water itself exerts pressure on the pipes. Thus leaks are typically of the water getting out and not contamination of the water (most of the time, anyway.)

Contamination rarely happens outside of the source of supply, and not somewhere along the pipeline.

Water pipes are under pressure. So outside water and pollutants do not infiltrate into leaky pipes. Unless you have a water shutoff. But those situations are minimal.

> I wonder how much human health is impacted by these leaky pipes.

Not much, because the water mains pressure keeps nasty things from entering the pipe.

However, when the system is depressurized due to a power outage or due to running out of water, nasty things can happen (stuff entering the water pipes, oxygen from air bubbles causing rust), and that's why after such events boil-off orders are issued for a few weeks afterwards until it can be reasonably assumed that all pipes have been flushed and all air bubbles have gone.

For what it's worth, utilities do care quite a bit about leaks (it's service they are providing which they can't bill for!) and use various testing apparatus to locate leaky parts of underground systems for repair and replacement.

Considering the difficulty and cost of repairing underground anything, most of which will be there for many many decades, it's never going to be perfect, but there's a lot of resources that do go into improving this.

Alameda county does something similar for health reasons. All home sales require pressure testing the sewer lateral. With replacement required if it fails before the deed can transfer or a loan is funded.

Those leaks are 99.9% one way.

We already have this data in a way, from cities where there is no running water and people rely on bottled water for drinking and washing.

For those wondering how big this is, that's about (80 meters)^3.