NDS 41P8 PVC S&D Cleanout Plug, with 4-Inch MPT Connection, Works with 4-Inch FPT drain fittings attached to Sewer and Drain Pipe, White

Why I bothered to test a simple cleanout plug

I didn’t expect a humble cleanout plug to merit a write-up, but a cracked cap at my curb cleanout opened a can of problems—odor, insects, and a clear path for debris. Swapping to the NDS 4-inch cleanout plug was supposed to be a 5‑minute fix, and it was. What surprised me was how much small design choices matter in something this basic: thread fit, material stiffness, UV stability, and even the size of the head you grab with a wrench. After using it through a hot season with sprinklers, sun, and lawn equipment, I’ve got a solid handle on where it shines and where to be cautious.

What it is

This is a 4-inch male pipe-threaded PVC cleanout plug designed for sewer and drain (S&D) systems. It screws into a female threaded cleanout adapter to seal the line and can be removed to access the pipe for inspection or to run a snake. Important note: it’s meant for S&D fittings, not DWV Schedule 40 systems. If your cleanout fitting is DWV (ASTM D2665), this isn’t the plug for you.

The cap itself is white, with a broad, slightly domed face and a raised square head for a wrench. The cap diameter is larger than the nominal pipe size—mine measured about 5.5 inches across the face—while the threads are the correct “4-inch” size. That mismatch in apparent sizes is normal for cleanouts.

Fit and compatibility: the part that matters most

Installation took me under five minutes, but that’s only true if you’re threading it into the right female adapter. Here’s how I verified compatibility:

• I checked the markings on the existing cleanout adapter. S&D fittings are usually labeled as such and often come from landscape drainage lines; Schedule 40 DWV is typically part of the home’s interior drainage stack or a more robust exterior riser.
• I dry-fit the plug first to check engagement. The plug should pick up threads easily by hand without rocking or cross-threading. If you have to force it from the start, stop—it’s probably the wrong thread standard or a damaged adapter.

On a clean S&D adapter, the plug engaged smoothly and seated square. I wrapped the plug’s threads with two wraps of PTFE tape (clockwise, so the tape doesn’t unravel as you tighten), then hand-tightened and gave it another quarter turn with an adjustable wrench. That was enough to seal without stressing the female fitting.

Tip: Avoid aggressive paste sealants that aren’t rated for PVC. PTFE tape or a PVC-safe thread paste is safer and plenty effective.

Build quality and materials

The plug is injection-molded PVC with UV inhibitors. In practice, that means it resists chalking and brittleness from sun exposure better than plain PVC. After a full summer of direct sun in a hot climate, mine hasn’t turned chalky or hairline-cracked. The face is smooth with clean molding and no flashing.

The face thickness is adequate for a cleanout—this isn’t a load-bearing piece—but the square drive head is the stress concentrator. If you overtighten, torque will focus at the head and can crack it on any plastic plug. Using a wrench that fully captures the square (not just the tips) and stopping at “snug plus a bit” avoids trouble. I wouldn’t use a cheater bar or impact driver here.

In side-by-side comparison with other commodity cleanout plugs, the NDS plug’s head didn’t feel flimsy, but it’s still plastic. If you expect to remove and replace it frequently (camera work, regular jetting), a brass or reinforced option might be worth considering. For typical residential access a few times a year, this PVC unit is more than sufficient.

Sealing and odor control

A clean thread engagement and light sealant are all that’s needed for a gas-tight seal in a gravity drain environment. Once installed, the plug stopped the faint sewer smell around the riser immediately. After irrigation cycles and a couple of heavy rains, I didn’t see any standing water in the riser or weeping around the threads. The plug’s broad face sheds water and makes it easy to spot if it ever loosens.

If your female adapter threads are nicked or deformed, no plug will seal perfectly. In that case, clean the threads with a nylon brush and flush with water, then try tape plus a compatible paste. If the adapter is cracked, replace the adapter rather than over-torquing the plug to compensate.

In use: access and removability

The square head accepts an adjustable wrench or a large crescent. It’s big enough to get leverage but low-profile enough not to snag mower wheels. I tested removal after a few weeks to simulate a typical service call; with tape on the threads, the plug broke free predictably without squeak, stick, or galling. Re-application of fresh tape and a wipe-down of the threads kept installation repeatable.

If your cleanout is flush with grade and sees a lot of mower traffic, consider a protective collar or a recessed cap box. The plug will tolerate incidental bumps, but a direct hit from a spinning mower blade is still plastic versus steel.

Weather and UV performance

Sun, sprinklers, and temperature swings are the enemies of outdoor plastics. The UV inhibitors here do their job. After months of exposure, color and gloss remained consistent and the plug didn’t soften or warp. That’s more than cosmetic—UV degradation often starts as surface chalking that leads to embrittlement at the square head. I didn’t see signs of that.

One caveat: white shows dirt. A quick wipe restores it, and the bright color is actually an advantage when locating the cleanout in turf or gravel.

Installation tips

• Verify your system: S&D vs. DWV. Read the lettering molded into the existing fitting.
• Clean the female threads with a brush and water; remove sand and grit so you don’t grind the threads.
• Use 1–2 wraps of PTFE tape or a PVC-safe thread sealant. Don’t mix both excessively.
• Hand-tighten until seated, then add a quarter to half turn with a wrench. Stop if the resistance spikes suddenly.
• Recheck after the first week if the area is high-traffic or newly backfilled.

Where it falls short

• Not cross-compatible with DWV Schedule 40 systems. That’s by design, but it’s an easy mistake to make.
• The plastic square head can be damaged by over-torque or the wrong wrench. A full-contact adjustable wrench is kinder than pliers.
• If your application involves frequent removal or high abuse, a metal plug might be a better long-term choice.

Who it’s for

• Homeowners and techs working on landscape drainage and S&D cleanouts who need a straightforward, weather-resistant plug.
• Anyone replacing a broken curb or yard cleanout cap and wants a quick, reliable seal against odor and debris.
• Users who want easy access for snaking or inspection without dealing with specialty tools.

If you’re servicing interior DWV cleanouts, skip this and match a DWV-rated plug instead.

The bottom line

The NDS 4-inch cleanout plug does exactly what a cleanout plug should do: thread in smoothly, seal reliably, survive sun and sprinklers, and come back out without a fight. Installation is intuitive, the material holds up outdoors, and the design strikes the right balance between accessibility and durability for typical residential use. It’s not a universal plug—DWV users need a different spec—and you do have to respect the limits of a plastic square head. But used as intended, it’s a dependable, low-cost fix that avoids bigger headaches.

Recommendation: I recommend it for anyone with a 4-inch S&D female threaded cleanout adapter who needs a durable, serviceable cap. It installs in minutes, seals odors and debris effectively, and stands up well to weather. Just verify your system type and avoid over-torquing during installation, and it should serve you for years.