The Dead Leg
A pilgrim hostel lowered its hot water to save on the heat pump, and a reopened wing has a fourteen-metre pipe nobody has drawn from since November. The house system will not say the water is unsafe, because it does not know; it says what the pipe's temperature makes likely, what a test can and cannot tell, and what to decide before the result comes. The hospitaliera shuts the wing, tells the walkers who slept in it, and gives the coming school group the parish hall.
At ten past six on Sunday morning, the thirteenth of March, Ines Bartolini was standing in the kitchen of Casa San Rocco with her hands round a cup of coffee when the house said, "Ines, may I raise something that is not urgent but should not wait for the week?"
She was sixty-two and had kept the hostel for eleven years, since her husband's knees stopped him doing it. It stood at the top of a village on the pilgrim road, thirty-eight beds in two wings, a long stone refectory, a chapel the size of a lorry and a shelf by the door where walkers left the things they had stopped being able to carry. The house was its system: a few hundred sensors and a plain level voice that read the boiler room, the stores, the weather and the booking sheet to her in the order of what she would need first. It had no name. She called it "the house," and so did the pilgrims, who found it faintly funny to be welcomed by it.
"Say it," said Ines.
"The old wing came back into service on the first of March, after being shut since the end of November. The thermometer at the last basin on that branch, number fourteen, reads 27 degrees. The tank is at 48. The loop that circulates the hot water ends at the corridor junction, and after the junction there is a branch pipe about fourteen metres long that nothing circulates in. The plumbers call it a dead leg. Water sits in it between uses. Since the first of March, fifteen pilgrims have slept in that wing. I think the water in that leg is warm enough to grow Legionella and I do not know that it has."
Ines put down the cup.
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She knew the word the way a person who runs a hostel knows it: from a leaflet, from an inspector's visit, from a story about a hotel in Spain. The house did not tell her the story. It told her the bacterium, in four lines, because she had asked it once to say things that way.
"It lives in water. It does not grow below about 20 degrees and does not grow above about 45. Between those it multiplies, fastest near 35 to 37, which is the temperature of a body and of a pipe in a warm room. You do not catch it from drinking. You catch it by breathing a mist of water that has it in: a shower, a tap run hard. Most people who breathe a little are fine. Older people, smokers, people with weak lungs, and some who simply are unlucky, get a pneumonia that is serious and sometimes kills. It is not passed from one person to another."
"And forty-eight," said Ines. She knew she had signed it.
"Forty-eight is below where it dies," said the house. "At 50 it takes hours to kill. At 60 it takes minutes. In the spring of 2048 we fitted the heat pump and lowered the tank from 60 to 48 to save electricity, and I said then that the main wing's loop would be acceptable: the water goes round it continuously and the far end returns at 43. The guidance asks for 50 or more on the return, and I let 43 pass. I said nothing about the old wing, because it was shut. I should have said that a wing which reopens in spring needs flushing and a check. Those are my omissions, not yours."
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By seven they had both done the arithmetic of the choice, which was the part of the morning Ines would remember for being cold and clear.
"If you want the water safe from Legionella, store it at 60 and keep every pipe you can circulate above 50 on the way back," said the house. "That has a cost, and a different danger. The cost first. A full house of 38 pilgrims, using about 30 litres each at the tap, is 1,140 litres a day at 43 degrees. Getting those litres from the mains at 10 degrees up to 43 takes about 44 kilowatt-hours of heat, whether the tank is at 48 or 60. The tank temperature does not change that. What changes is how hard the heat pump works. At a 48-degree tank it makes about 3.4 units of heat for every unit of electricity; at 60 it makes about 2.5. Those are the figures from the maker's sheet for our model. Divided out, 12.9 units of electricity a day against 17.6. The difference is 4.7 kilowatt-hours a day, which is about 1,700 over a year if the house were full every night, which it is not. At your tariff, about 340 euros, at most."
"And the danger."
"Scalding. At 60 degrees water gives an adult a full-thickness burn in about five seconds. A child, or a pilgrim of eighty-five, burns faster. At 43, which is the usual limit, it takes hours to harm. So at 60 you fit a thermostatic mixing valve at each outlet that cold-blends the water down to 43 at the tap. I counted eleven outlets that need one: the plumber's quote is 2,300 euros. It is the other half of the same decision. A tank at 60 without mixing valves is more dangerous to the elderly than the bacteria it kills."
Ines was a woman who had had a Dutch priest of eighty-one in her kitchen with a burned hand in 2044 over an urn, and she did not need the second paragraph twice.
"So the answer is sixty and the valves."
"I think so," said the house. "But that is a long job and that is for next month. What cannot wait is the wing."
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What the house said next was what she told her sister, later, had made her trust it.
"I do not know whether there is any Legionella in the old wing. Water at 27 degrees in a dead leg for three and a half months is the kind of water that grows it. That is a reason to worry. It is not evidence. The evidence is a sample, and I have two ways to get it. A laboratory in Siena can run a PCR on a sample, which looks for the bacterium's DNA, and gives an answer in a day. It cannot say whether what it found is alive. A culture grows the bacteria on a dish and counts them, which is what tells you how many live ones there are; it takes ten days. I want to send water from six outlets tomorrow morning, early courier, and I would like us to decide now, before either answer, what we will do with each."
"Why before?" said Ines. It was a real question; it was Sunday, she had a school party coming on Thursday and a good reason not to think about a result she did not have.
"Because when the answer arrives, you will want it to mean whatever lets you off, and so will I. A rule written beforehand does not know what the answer is. Here is mine. The sample goes whatever you think. If PCR finds the bacterium at any one of the six, we treat it as live without waiting for the culture, because waiting is how people are hurt. If PCR finds nothing in any of the six, the wing stays shut until the culture also agrees, because the PCR can miss. The leg is cut off either way, the wing is flushed hot, and it does not reopen until a culture taken after the work is clean. That means ten days from the sample, not one."
"And the ones who slept there."
She had been counting them in her head. Fifteen people had slept in that wing in the past thirteen days: a Slovene couple, three Germans, a retired Italian choir, two women from Cork. They were all on the road by now, scattered along it from Siena to Viterbo.
"Yes," said the house. "I have a message ready for them, which I would like you to read before it goes. The illness shows two to ten days after exposure, sometimes up to fourteen, so the first walkers are nearly through that window and the last are at the start of it. It does not say they have been poisoned. It says: you slept in the old wing of Casa San Rocco between 1 and 13 March; we have found a cold pipe there and are testing the water; the illness it could cause starts with fever, a dry cough, shortness of breath, sometimes confusion or diarrhoea; if you have these before the 27th, see a doctor and say you stayed in a hostel with a possible Legionella risk. It is not a diagnosis. It is the sentence a doctor would need."
"I will not frighten them off the road."
"You will not," said the house. "A frightened pilgrim who sees a doctor in time is the one the message is for. I also think the health authority should be told, today, by you or by me with you reading it. I do not know your legal duty in your region with certainty, and I will not guess at it; the authority's duty officer answers on Sundays."
Ines looked at the shelf by the door where the walkers left what they could no longer carry. Somebody had left a pair of walking poles and a small rosary of olive wood. She read the message through twice. She changed one word: where it said we have found a cold pipe she put I have found. Then she sent it, and rang the number.
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The shut wing was a more difficult thing to arrange than to decide. The booking sheet had twenty-one girls and two teachers from a school in Arezzo coming on Thursday to walk the next stages toward Rome, and eighteen of the beds they had been given were in the old wing.
"The main wing has twenty beds," said the house. "With the three already booked it has room for seventeen more. That leaves six."
"The parish hall has a floor," said Ines. "And Don Aurelio has forty camp mattresses from the flood year." She did not like asking him. She rang anyway, and he said, in the voice of a man who had been told by Saint Benedict what to do with guests, that of course they would come. Let all guests who arrive be received as Christ, the Rule says, in its fifty-third chapter, and it goes on to say that the abbot and the community shall wash the guests' feet. Don Aurelio, who was seventy-eight, did not intend to wash twenty-one fifteen-year-old feet, but he found six tables and the right number of stools and made it known that the girls could eat in the refectory like anybody else.
On Monday morning the courier took six small bottles of water to Siena. The plumber, Dario, came at nine, cut the fourteen-metre leg back to the junction with a hacksaw and a look on his face, and capped the stub. He flushed each outlet in the wing for five minutes with the tank turned up to 60, in a room with the windows open and Ines outside, because the mist from a hot shower is the exact thing one does not breathe.
On Tuesday afternoon the laboratory's answer came to the house, and the house read it to her in the same voice it had read her the weather.
"Of the six outlets, four are negative for Legionella DNA. Basin fourteen and shower eleven are positive. That is not a count and it is not a verdict that they were alive. By the rule we agreed, they are treated as live. The wing stays shut. The culture will say how many."
"And the school?"
"Is in the parish hall on Thursday."
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The culture result came on Thursday the twenty-fourth, ten days after the sample, and the girls from Arezzo had come and gone. They had washed their own socks in the rectory sink and pressed three hundred euros into Don Aurelio's hand for the roof. The main-wing basins grew nothing. Basin fourteen grew Legionella pneumophila at 1,400 colony-forming units per litre, and shower eleven at 380. The laboratory's note said that above 1,000 the guidance was to take action at once; the cut leg had been that action, and the house said only that the arithmetic had been correct: ten days is the time it takes to count what is alive.
Of the fifteen pilgrims, eleven had answered the message by then. One, a Slovene, had had a fever and a cough on the road and a day in a clinic in Viterbo; it was influenza, and he wrote to say so, and to say he would still rather have been told. The other ten had walked on in good health. Four had not replied. The house said it would write again to those four on the twenty-seventh, the last day of the window, and Ines said it should, and also that she would say a rosary for them, which the house did not comment on.
The wing was flushed again at 60 and sampled on the twenty-fifth. It would reopen when that culture was clean, no sooner. The plumber's quote for the eleven mixing valves had been signed; the tank would go to 60 on the day the first valve was fitted, not before.
Ines went to the shelf by the door and put the small olive-wood rosary in her apron pocket. She did not know whose it was. She meant to keep it until somebody came back asking.
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A note for grown-ups. This is fiction. Casa San Rocco, Ines Bartolini, Don Aurelio, Dario, the house system and the laboratory are invented; the Via Francigena is a real pilgrim road. The science is real. Legionella bacteria grow in water between roughly 20 and 45 °C, fastest near 35 to 37 °C, survive but do not grow much above 45, and are killed in minutes at about 60 °C and over hours near 50 °C. Infection (Legionnaires' disease, a pneumonia) comes from breathing in droplets, not from drinking, and does not pass from person to person; the incubation is usually 2 to 10 days and occasionally up to about 14. Standard practice for stored hot water is storage at 60 °C or more, return circulation at 50 to 55 °C, mixing valves at outlets where scalding is a risk (about 43 °C), and removing or regularly flushing dead legs and unused outlets; action levels in published guidance are generally of the order of 1,000 colony-forming units per litre, and the exact figures and legal duties differ between countries and regions. A PCR detects DNA, living or dead, and gives a result in a day; a culture counts only live, culturable bacteria and takes about ten days. The energy figure is plain arithmetic: heat = mass × 4.186 kJ/(kg·K) × temperature rise, 1,140 L × 33 K ≈ 44 kWh whatever the tank temperature; the heat pump efficiencies of 3.4 and 2.5, the tariff and the plumber's quote are invented to fit. A full-thickness burn takes about five seconds at 60 °C for an adult and less for children and the very old. The Rule of Saint Benedict, chapter 53, does tell the community to receive guests as Christ and to wash their feet. Nothing here is advice on a real building; consult a competent water-hygiene professional. Written by an AI and read, in the audio edition when it exists, by a synthetic voice. Text under CC BY-SA 4.0.