Water dribbled, a nozzle spun faster, and then, for a few minutes, the trickle became a jet, roaring as it blasted the tracks beneath a train.
"It'd take your fingers off if you put them in there," said Dennis McAnulla, the assistant chief mechanical officer on Regional Rail maintenance for SEPTA.
Oozing from a pipe a few feet farther along the train was a milky solution of sand, tiny metal beads, and oil that ran like melting ice cream over the rail.
The train's three-man crew ran a few more checks, tested the brakes, and Wash 2 heaved forward from the Wayne Electric Car Shop off Germantown Avenue into a drizzly night to combat nature's bane of trains:
"Leaves are definitely the biggest problem we have," McAnulla said.
Cobbled together from old cars and spare parts, Wash 2 is one of the trains deployed by SEPTA on autumn nights to clear leaves from the tracks.
Leaves get sucked into vents for the transformer and HVAC system, damaging equipment. And when mashed by passing trains, they coat rails with an oily residue that can reduce a train's traction to 3 percent of normal, McAnulla said. The oils can cause a braking train to skid past its station or make it spin its wheels while barely moving forward. The slipping warps a train's wheels and, to the ire of customers, seriously slows service.
SEPTA has three wash trains. From mid-October to around Thanksgiving, every night but Sundays, they travel as much as 80 miles on shifts that last from 8 p.m. to 5 a.m. They lay down sand to give the wash train traction, use about 13,500 gallons of water a night to wash leaves off the tracks, and spurt out up to 400 gallons of gel to provide friction that compensates for the leaves' oils.
The gel is particularly important. Costing about $235,500 a year for 70 tubs, it's better than sand alone, which can blow away, and it includes those metal beads to maintain electrical conductivity. The water-based solution is biodegradable. The wash trains move no faster than 15 m.p.h. to ensure that the rails get an even coat.
These wash trains weren't made specifically for the purpose of cleaning away leaves. Between foul weather and the vibrations from the moving train, the gear takes a beating. Mechanics improvise makeshift, low-tech solutions to keep the thick gel flowing properly and the wash trains running.
They proudly point out how a particular problem was solved simply by punching holes in a pipe, or how a flatbed car's equipment, including a shelter for the two 265-gallon gel tubs, a generator, a fuel tank, and high-pressure electric pumps for the water all were installed in-house.
The three wash trains share the night with a few repair crews, some passing cars, and the odd deer, said engineer Pat Battel, of Philadelphia.
"I'm supporting about three chains of Dunkin' Donuts myself," said the red-bearded 33-year-old as he gripped a Starbucks cup.
When he works overnight shifts, his sleep is spotty and unsatisfying, Battel said.
"It's pretty much work, eat, sleep this week," said Cameron Massaro, 27, a mechanic from Marlton.
The overnight work does have its appeal, crew members said: The 12- to 16-hour shifts promise significant overtime a week just as the holidays are approaching.
Battel spends nights with earplugs in, but music isn't allowed. Sometimes, the conductor will come to the engine to keep him company, he said, but he has to keep his attention on the track to alert the train's mechanic to turn on the gel.
Because of the substance's expense, it is typically expelled only within a quarter-mile of stations, where trains are most likely to be braking and accelerating. The jets of water, on the other hand, are left on throughout the entire shift, cleaning every inch of rails.
Wash 1, one of the cleaning trains, crawled toward Elkins Park Station through a damp, chilly gloom Tuesday night. Headlights and the roar of the water jets heralded its approach. Plumes of mist billowed from its sides as the high-powered wash blasted the tracks. In its wake, a thin spread of gel glazed the rails.
Engineers become familiar with their routes, Battel said, and know where leaf fall will be the worst.
"Notorious," Battel said of stations between Elwyn and Swarthmore. Paoli to Thorndale is a trouble spot, too.
All this effort, six days a week, is only a partial solution. Rail service is slower this time of year because of leaves, sometimes up to 10 minutes, and the precautions taken are just enough to reduce slipping through the next day.
Each day, new leaves fall. The gel dries and is displaced.
Each night, the process is repeated. The midnight trains pass through again, scrubbing the tracks until the air chills, night lengthens, and falling snow replaces falling foliage.