A holding-tank hose permeation case

S/V Persephone, a 1991 Tartan 37 whose owner has wintered her at the Boat Haven inner basin since 2018, has had a recurring complaint since the 2023 cruising season: a noticeable smell in the saloon and forward cabin, worse in summer than in winter, worse when the head had not been pumped recently, but persistent year-round. The owner had taken the boat to three different yards before us — one in Anacortes, one in Seattle (a brief consultation), and one in Sidney BC during a summer cruise — and each yard had proposed a different fix.

The first yard replaced the vent-line filter (it had been original to the 1991 install, never replaced). The second yard rebuilt the manual head. The third yard inspected the holding tank for leaks (none found) and recommended a new macerator pump. The owner spent approximately $2,100 on diagnostic and repair work between 2023 and the summer of 2025. The smell persisted.

By mid-December 2025 the owner was, in her own description, "ready to sell the boat." She called the shop on the evening of Wednesday 17 December 2025 (a Wednesday in the snow, the boatyard closed for weather), and asked whether we could see her on the Friday. Salla took the appointment.

The wet-rag test

Salla arrived at the boat at 0830 on Friday 19 December 2025. She did not look at the head. She did not look at the tank. She did not look at the macerator. She looked, instead, at the run of sanitation hose between the head and the tank, which on a Tartan 37 runs under the V-berth, along the port side of the chase, around the mast step, and aft into the lazarette holding tank. The total run is approximately 8 linear feet.

She took a cotton dish-rag, wet it with hot water, and wrapped it around the hose for thirty seconds at a half-dozen locations along the run. Then she smelled the rag at each location. The standard procedure, published by Practical Sailor in 2018, is that if the hose has permeated, the rag will pick up the smell of the hose's contents through the wall of the hose; if the hose is intact, the rag will smell only of warm cotton.

The rag, at every location Salla tested, smelled. The hose had permeated along its entire length.

The fix

The hose on the Tartan was a generic vinyl sanitation hose — we cannot tell the original manufacturer from the markings, which have abraded off — that had been installed by the boat's previous owner in 2018, before our shop's relationship with the current owner began. The current owner had assumed, reasonably, that a seven-year-old hose was new enough not to need replacement. The first yard had not suggested checking it. Neither had the second or the third.

The replacement is 9 feet of Trident 101-series sanitation hose, the same hose we have used on every Type III install since the 2018 Practical Sailor test that ranked it at the top for permeation resistance. The cost is approximately $58 in materials and $480 in labor across two working days (the labor is in the routing — pulling the old hose, fishing the new hose through the same chase, double-clamping with all-316 stainless at every fitting, verifying no kinks at the long-radius bends).

The boat was returned to her slip on Wednesday 23 December 2025. The owner called the shop on Friday 2 January 2026 to report that the smell was gone. Her note: "I cannot believe I lived with this for three years."

The lesson

The lesson is for the trade as much as the owner. The wet-rag test is the first diagnostic on any cabin-smell complaint that has been around longer than a single pumpout cycle. It is the test we ourselves should have suggested when she first called in 2023, but at that point her boat was being seen by another yard and we were not consulted. The lesson, also, is that hose permeation life on a generic vinyl sanitation hose is closer to 3–4 years than to 7. The lesson, finally, is that an owner who has been told three different things by three different yards is an owner who needs the simplest diagnostic test first, before any further parts are bought.

For the standing reference on hose materials, see the MSD primer in this issue. For the back-catalog Daybook entry on a similar case (Vol. III No. 2, June 2023 — a Catalina 30 with the same diagnosis), see the bound back issues. — L.B.