
Drinking Water Is Staying in Pipes Longer - pseudolus
https://www.citylab.com/perspective/2019/05/water-pipes-infrastructure-shrinking-cities-health/590752/
======
sbierwagen
The article doesn't specifically say how much time water spends in pipes,
(Minutes? Weeks? Months?) but the linked paper does:

>A utility in North Carolina serving 300,000 customers with 1,100 miles of
main calculated water ages ranging from 2 to 75 hours throughout the
distribution system using a fluoride tracer study (DiGiano, Travaglia and
Zhang 2000).

> A Midwest utility with a service population of 800,000 and 2,750 miles of
> main recently found based on a hydraulic model that the water age in the
> distribution system was typically less than 80 hours while several sites
> exhibited a water age up to 150 hours (Vandermeyden and Hartman 2001).

> One California utility found water ages exceeding 400 hours in certain areas
> of the system, particularly dead end areas, under minimum day and average
> day demand conditions (Acker and Kraska 2001).

> A Canadian utility serving 24,000 people with 86 miles of main estimated
> water age using a hydraulic model and found that dead-end nodes had a water
> age ranging from 300 to 600 hours under average day demand conditions
> (Prentice 2001).

"How long is too long?" It depends, apparently, on what the pipes are made of,
how old they are, how corrosive the water is, (Which is what caused the Flint
disaster) etc.

~~~
nullwasamistake
Wow. 600 hours is 25 days, that's far too long. The chlorine used to sterilize
the supply will be long gone by then.

~~~
zackmorris
Not necessarily. Many municipal water treatment plants are adding or switching
to chloramines, which can be more stable than chlorine gas:

[https://en.wikipedia.org/wiki/Chloramine](https://en.wikipedia.org/wiki/Chloramine)

The main problem is that they are potentially more carcinogenic.

The rarely talked about, but potentially more serious problem, is that
chlorine and chloramine are difficult to remove from water by letting it stand
or boiling it:

[https://www.sfwater.org/Modules/ShowDocument.aspx?documentID...](https://www.sfwater.org/Modules/ShowDocument.aspx?documentID=6920)

[https://www.physicsforums.com/threads/does-boiling-water-
rem...](https://www.physicsforums.com/threads/does-boiling-water-remove-
chloramine.857730/)

[https://www.morebeer.com/articles/removing_chloramines_from_...](https://www.morebeer.com/articles/removing_chloramines_from_water)

It looks like activated charcoal filters are the best way to neutralize it,
but I'm having trouble finding numbers for how effective they are at it.

[https://homebrew.stackexchange.com/questions/3447/what-
are-t...](https://homebrew.stackexchange.com/questions/3447/what-are-the-
various-ways-to-remove-chlorine-chloramine-from-tap-water)

------
rayiner
Our water infrastructure isn’t in a shambles just in shrinking cities. It’s a
disaster everywhere:
[https://www.infrastructurereportcard.org](https://www.infrastructurereportcard.org).
It’s an archetypal example of how the government is bad at setting prices.
Water boards respond to public pressure, and as a result set rates too low to
be sustainable in the long run: [https://bipartisanpolicy.org/blog/stretching-
water-dollars-f...](https://bipartisanpolicy.org/blog/stretching-water-
dollars-further).

> Despite the challenges posed by shrinking federal investment and rising
> costs, America’s water systems strive to maintain affordability. As such,
> many water systems have historically underpriced the services they provide
> to keep water rates low.

The result is a backlog in investment approaching a trillion dollars.

~~~
natermer
This is just a microcosm of problems governments are going to face with
shrinking populations.

Another, related problem, is the issue of maintaining state pensions and other
entitlement programs.

Social Security in the USA, for example, has a negative ROI. For it to work
the government has to take money from younger working people in order to pay
for older retired people. As the population shrinks you have less and less
young people being forced to support the larger number of retired people.

All these sorts of programs have the same problems. They were designed in a
era were it was assumed that people died off as a higher rate and people were
born at a faster rate. As those trends gradually reverse then all
welfare/entitlement programs are becomingly increasingly insolvent.

....

This sort of stuff is why the Soviets had to institute travel restrictions and
a sort of passport system in the USSR; you can't have effective long term
government planing with a rapidly shifting population.

~~~
vkou
> Social Security in the USA, for example, has a negative ROI. For it to work
> the government has to take money from younger working people in order to pay
> for older retired people. As the population shrinks you have less and less
> young people being forced to support the larger number of retired people.

You can solve that entire problem with a few years of inflation. There's
nothing, in principle, wrong with a guaranteed return-until-you-die
investment, as _part_ of a retirement strategy.

It's a smart part of a diverse retirement portfolio (Especially when compared
with a 100% commitment to the guaranteed-contribution, variable-return
investments of 401ks). I wish I could invest more than 3% of my income into SS
- and I _expect_ to take a haircut on that investment.

~~~
bluGill
There are inflation indexed annuities that you can invest in. Most 401ks don't
have them directly, but when you retire I advise my friends to move some of
your saving into them: enough to cover the basic life expenses (insurance,
food, rent). Because they are for life they are typically lower return on
investment, but they lower the risk of living wrong so they should ensure you
can afford at least the basics of life.

~~~
vkou
Sure, and I'll probably look into them, if, by retirement, the world doesn't
turn into a Mad Max hell-scape. (Which I am not optimistic about.)

The thing is, all the same risks of Social Security (People living longer than
expected, investment returns being lower than expected, a prolonged recession
emptying out the fund, inflation turning your guaranteed returns into 'only-
good-as-toilet-paper-money') apply to them, but even moreso (Because they
cannot count on continued buy-in, unlike Social Security).

------
lbutler
I build hydraulic models of water systems for UK utilities (but live in
Canada), one of the things we look at in the model besides the performance of
the network is the age of water.

In the UK, pipes are sized based on the needs of the domestic demand, while
capacity for fire flow is not considered. While in North America the opposite
is done, where the network, including capacity in tanks and pressure within
the network, must take into account fire flow requirements. (The attached EPA
document goes into this in more detail)

While a UK residential street may be supplied by a 100mm main, the same street
in the US may need a 200mm main. That's a four-time increase in volume that
needs to be turned over in the pipe for just a little street!

I have seen design documents for North American towns requiring flow rates of
50-90l/s to protect a single house. When I tell my colleagues in the UK about
this they laugh and ask if I'm joking and if the fire bridge is aiming to
simply flatten the house to stop the fire.

Pressures in North American networks are also higher than in the UK, once
again to meet fire flow requirements, which leads to higher background leakage
and bursts within the network.

High age of water is an issue that will affect most North American water
systems regardless of if they are shrinking or growing.

------
myself248
As I commented on their own comments section:

The only graphic in this article is "city shrinkage", which is then conflated
with water age, which is then related to water problems. But I suspect these
things may not be as linearly connected as the authors imply, specifically
because of factors like the chemistry of incoming water, as exemplified by the
Flint situation.

Also, water systems can have vastly different flow rates, pipe sizes, and
other parameters that influence water age, not just population change.

So, is there better data? Can we actually show a relation between city
shrinkage, water age, and water problems? If this data exists, why wasn't it
presented? If this data doesn't exist, why is a relationship suggested?

~~~
thomas
Water data is hard to come by, not updated frequently, and generally not
sampled at the place there want it to be from unfortunately. Lots of water
data here: [https://mytapwater.org](https://mytapwater.org) and
[https://www.waterqualitydata.us](https://www.waterqualitydata.us)

------
assblaster
Isn't the solution to this just to have a connection from tap to sewer if a
certain flow rate is not maintained?

~~~
natermer
You would just shift the costs away from maintaining pipes to treating massive
amounts of water that would never get used by anybody.

And you will still have to maintain the pipes. Your solution would reduce
costs per mile, but you still have a lot of mileage to maintain with a
shrinking population.

~~~
amluto
I would believe that there are areas where something like this, perhaps for
groundwater recharge, wouldn’t be totally crazy.

------
peterwwillis
This may be a short-term issue, versus the long-term issue of not having
enough fresh water to drink. Scientists have been warning about this for a
while now. We can probably advance the technology of purifying water to make
it cheaper and more widespread, but we can't solve getting enough fresh water
just by inventing a new gadget.

To keep from running out of fresh water, we'd need to stop growing the
population, or stave off the amount of water used for agriculture, or re-
engineer all our wastewater systems for treatment and reuse, or build massive
amounts of expensive desalination plants along with a massive global
distribution network. All of these are possible, but we also have to actually
start the process before it becomes too painful.

