You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
So what’s the mechanism from this cold weather that’s causing the mains supply pipes to leak so much. I’m assuming the pipes are below the depth that frost can penetrate (typically assumed to be 450mm in the UK) and the water in the pipes is usually flowing. Is it just a bit too contraction along the pipe length?
Cast iron pipes expanding too fast with all the expansion sleeves jammed up from 120 years of being buried.
Rapid temperature changes put them under a lot of stress.
I would anticipate that the ground surrounding the pipe would act as a buffer and smooth any sudden temperature changes. Or do you reckon its the temperature of the water entering the pipe ?
The issue is ground heave due to the thaw process, a prolonged freeze followed by rapid thaw causes lots of ground movement that rigid cast iron or asbestos cement pipes are vulnerable to. Badly laid plastic is also vulnerable due to typically poor quality control of contractors.
The temperature of the water in the pipes isn't an issue as it only varies by a few degrees over a full year and the pipes are too deep (750mm plus) for much of a temperature change due to surface conditions. The pipes themselves are temperature controlled by the water flowing through them.
I was thinking about this myself, presumably countries with generally colder weather don't have the same issues (on such a widespread scale) so I guess they lay their underground pipes with additional protection or something (or using a different pipe material)? Also how do trains work colder countries, are the points there heated? Everything seems to come to a farcical halt in this country with a short spell of bad weather - are we just cheapskates or just following sensible economics and specifying/building for the average not the exception?
Other countries have lots of leaks, you just don't hear about them
With legacy infrastructure and slow pace of renewal freeze thaw incidents are a fact of life. The volume swamps the available resources and there are always going to be challenges.
As for UK preparedness, ask how many emergency/ utility company/ NHS vehicles are fitted with all season tyres get about in the conditions?
Budgets are controlled by bean counters who do 9-5 and can work from home.
Victorian cast-iron pipes were never intended to last as long as they have or to bear the stresses they do from massive amounts of heavy traffic. This is one area of Victoran construction that was not over-engineered, unlike all the bridges, railways, canals, tunnels, sewers and other infrastructure that still benefits us nowadays becaue the Victorians didn't have computers so they engineered stuff far stronger than the minimum necessary.
Big n daft - Frost depth in UK is circa 0.45m bgl., so ground at / below typical pipe depth should never heave from freeze / thaw.
Globati - Agree completely, but the stresses from traffic don't increase when its cold, so shouldn't directly lead to more leaks following cold snap.
The Victorians didn't skimp on pipe and spend on everything else
The materials used age and there are particular corrosion mechanisms due to being buried and the water quality carried, unlike surface assets they are hard to maintain. There is still a lot of victorian pipe in the ground, you just don't see it.
Marcus, you are stating that there is no ground heave due to frost in the UK below 450mm
You also think the Victorians skimped on the water pipes they buried
I disagree
They've done pretty well to last over 120 years!
I'd say well over engineered.
They were designed with expansion sleeves to cope with temp changes / movement etc, just they corrode after 120 years underground and jam up, which increases the stress on the pipes.
Big n Daft - Not skimped, just beyond the end of their design life.
Happy for you to point me in the direction of engineering examples / CIRIA research, etc., which advises material below 450mm in the UK must be protected from frost. Everyday is a school day.
are we just cheapskates or just following sensible economics and specifying/building for the average not the exception?
A bit of both.
As for UK preparedness, ask how many emergency/ utility company/ NHS vehicles are fitted with all season tyres get about in the conditions?
Budgets are controlled by bean counters who do 9-5 and can work from home.
Ultimately the budgets are set by politicians, who normally get voted in after promising to lower your tax bill while still providing the same services. So when the budget for that service gets cut*, they have to make a decision about whether having all season tyres on ambulances in the south of England (that might not make any difference) at £150 a corner is worth it compared to cheaper £75/corner tyres that will only (maybe) make a difference 2 or 3 days out of every 3 or 4 years.
It's the same with NHS/police/fire service efficiency. You can use every single resource at 100% all of the time and be more efficient, but then there's a massive pile up or a terror attack or a flu outbreak and you've got zero slack in the system to be able to respond effectively. But run a hospital with 20% of beds empty at any one time and it's 'wasteful' for the majority of the time that there isn't something major going on. It's fine if you're on a production line churning out cars or something, you can tell your customers that there will be a long wait (see pretty much any 'factory order' popular car for proof that most people will accept it, if they didn't then they'd buy something else and there wouldn't be a 4 month wait for a new Audi) or put your prices up to balance supply and demand but public services basically give their services away for free while the people using it consistently vote for politicians who promise to give those services less money.
*Yes, there are a million ways of measuring it and then arguing about whether it's really a cut or not, % of GDP/£ per population/total £/£per taxpayer/growth per year etc etc.
marcus - useful summary of the causative mechanisms behind mains bursts in this recent UKWIR (UK Water Industry Research) 2017 report:
https://www.ukwir.org/doc/$UdHWgsG!
(hope the link works...)
Suggest you might want to check out bottom of page 12, 3d+e on page 13 and 3.2.3 on page 18 which all point to it being changes in the temperature of the water conveyed and the resultant longitudinal contraction/expansion being an isssue at joints (for cast iron and to some extent ductile iron mains).
Railways - most points are heated here in the UK. One big issue is with electric trains running on the third rail - freezing rain or snow sits on top of the rail and stops it working.
Marcus, you need to research how frost heave works, as stated above the pipes don't freeze as they are deep enough. The issues come from the pressure exerted by the freeze thaw/ frost heave mechanisms which are magnified by the presence of increased ground moisture due to minor leaks/ weaping joints etc where water pipes are present
As for insulation requirements you will know being an expert in this that Water Fitting Regulations as applied by Thames et al require pipes against an exterior wall including basements to be insulated this includes below 450mm
Handy link for you
You will similar examples on the twenty odd other water company websites
https://www.ukwir.org/doc/$UdHWgsG!
hmm - needs the “!” on the end which the link icon keeps snipping off!
Cheers drain - makes more sense than effects of the ground. I'll have read later.
If water temperature was a critical factor water companies would monitor it for leakage detection purposes it is a very easy to monitor parameter and has been for decades.
Additionally the small reservoir getting cold theory supported by Drain is great until you consider the large conurbations that have water sources 60 plus miles away, large service reservoirs tens of miles away etc plus the one for water to travel through the network would mean there would be a "stagger" whilst it travels through the network. Plus the size of the sources mean that the water abstracted is rarely > 10 deg. Finally how much variation in temperature due you get in borehole sources, does water 100m plus below ground vary in temp?
The issue with freeze thaw events is that they are difficult to get research data on as it's unlikely all parameters are covered and they don't happen every year. It is not that we don't have cold temperatures, it is the depth of the cold and the speed of the thaw that is a critical factor
water temperature is no doubt a cause of/ factor in leakage and bursts, it does not account for freeze thaw incidents