One of my 6-unit buildings used to back up at the ground-floor kitchen sinks about every 18 months, and each time a plumber charged me 35,000 yen to jet the line clear. After the third visit in five years I bought a compact electric drain jetter for 48,000 yen. I have used it twice a year since, and it paid for itself inside the first season. Jetting your own drain lines is well within reach for a hands-on landlord, as long as you respect where the DIY limit sits.
Why the grease builds where it does
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In a small stacked building the vertical soil stack rarely blocks. Gravity keeps it moving. The trouble is the near-horizontal branch runs under the ground floor and the buried lateral out to the public sewer, where the pipe sits at a shallow 1 to 2 percent fall. Kitchen fat cools and clings there, catches rice and coffee grounds, and narrows the bore over a couple of years until one bad night it closes. On my building the choke point was always the same 4m buried run between the last cleanout and the boundary. Older buildings often still have a drum trap, the round wan-torappu, under the kitchen or in an outdoor pit, and those collect grease faster than anything else on the line, so I clean them out by hand before I even start the machine.
Prepping the building before you start
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A jetter pushes water and pressure in every direction from the nozzle, so half the job is making sure it only goes where you want. Before I run it I close or weight the lids on every other cleanout and floor drain on that branch, put a rag in the ground-floor shower and washing-machine drains, and warn the ground-floor tenants not to run water for the next hour. I also check that there is somewhere for the flushed debris to actually go: if the public sewer connection itself is sluggish, jetting just moves the plug 3m and I have gained nothing. On a septic or a shared gappei-shori tank system I skip the enzyme treatment afterward because it can upset the tank bacteria.
The machine and the hose setup
I use an electric jetter that puts out about 150 bar through a quarter-inch hose. The nozzle is the key part: a button-nose sewer jet with one forward hole and three or four rear-angled jets. The rear jets pull the hose down the pipe and scour the walls on the way back out. My kit is simple:
- 150 bar electric jetter, quarter-inch by 15m hose
- Button-nose sewer nozzle plus a spare rotary nozzle for hard scale
- Foot valve so I can stop flow without leaving the pipe
- Wet-dry vacuum and rags for the inevitable splash-back
- Sealed goggles, elbow-length gloves, and boots
Working from the right access point
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Japanese drainage almost always has an outdoor cleanout, the souji-guchi, at each bend and near the boundary, usually under a round concrete or plastic lid. I start at the cleanout closest to the blockage and feed the hose downstream toward the sewer, never upstream toward the fixtures. I mark the hose with tape every metre so I know how far in the nozzle is, and I keep the water running as I withdraw so the debris flushes ahead of the nozzle rather than packing behind it. A full pass on that 4m run takes me about 25 minutes, plus 20 minutes of setup and clean-up.
The twice-a-year routine
I jet every branch and the main lateral in March and again in September, before and after the heavy-use winter. I run each line until the return water is clear for a full 30 seconds, feeding the hose in slowly and letting the rear jets do the pulling rather than forcing it. Then I withdraw it in stages, pausing every metre to let the loosened grease flush ahead. After the pass I pour two buckets of near-boiling water and an enzyme drain treatment down the ground-floor kitchens to slow the next build-up, and I note the date and how far the nozzle reached in the building file. Comparing that reach figure year to year is how I catch a slow narrowing before it becomes a blockage. Since starting this schedule I have had zero emergency backups in four years on a building that used to give me one every 18 months, and the two annual sessions take me about three hours total.
Where I stop and call a professional
The jetter clears grease and soft scale. It will not fix a structural problem. If the nozzle stops at the same point every time, if I pull back tree-root hair, or if a section of the run holds standing water after jetting, that points to a bellied or cracked pipe and I bring in a company with a drain camera, which costs about 25,000 yen for the inspection. On one older building that camera found a collapsed clay section under a parking pad, a 240,000 yen dig-and-replace that no amount of jetting would have solved. I also do not jet a line I have never seen mapped, because pushing 150 bar into an unknown junction can blow a seal on an old joint. Knowing the difference is what keeps DIY jetting from turning a small problem into a flooded ground-floor unit.
The machine lives on a shelf in my van now, and running it two weekends a year is one of the easiest maintenance wins across all 9 of my properties.
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