Tested: How to Get Asphalt Out of Water Filter Housings

By Tom Bradley · December 19, 2025

Immediate Action (first 5 minutes)

Finding black, sticky sludge in your drinking water is terrifying. I've inspected hundreds of compromised filtration setups over the last 12 years. Asphalt contamination usually happens after municipal pipe repairs or when driveway sealcoat leaches into a shallow private well. Shut off the main water valve immediately. Don't hesitate. If you leave the system pressurized, that toxic sludge pushes deeper into your reverse osmosis membrane. This turns a simple $20 filter swap into a massive headache.

Asphalt contains polycyclic aromatic hydrocarbons (PAHs). These are highly toxic. You cannot just rinse this stuff down the drain and hope for the best. Grab a 5-gallon bucket. Place it directly under your filter housing. Relieve the pressure by opening the nearest cold water faucet. I always tell my clients to treat this exact moment like a hazmat situation. Put on thick gloves. Keep kids and pets out of the room. The volatile organic compounds (VOCs) off-gassing from fresh tar can cause immediate respiratory irritation in enclosed spaces.

What You'll Need (tools/products)

You can't tackle petroleum-based stains with basic dish soap. I've tried Dawn on asphalt residue. It just smears the black gunk around the polypropylene housing, making a bigger mess. You need targeted solvents and heavy-duty gear. Here is my exact toolkit for this messy job.

Zep Heavy-Duty Citrus Degreaser ($8-12): This is my go-to. The d-Limonene in citrus solvents breaks down petroleum bonds without melting your plastic filter housing.
6-mil Nitrile Gloves ($15 for a box of 50): Standard latex gloves will dissolve when they touch asphalt. Buy thick, chemical-resistant nitrile.
Plastic Putty Knife ($4): Never use metal scrapers on filter housings. Metal gouges the plastic, creating microscopic grooves where bacteria will hide later.
Nylon Bristle Brush ($6): Get one with a long handle to reach the bottom of 20-inch Big Blue housings.
Pentek DGD-5005 Replacement Filter ($18-25): A standard 5-micron spun polypropylene sediment filter to replace the ruined one.
Dow Corning Molykote 111 O-Ring Lube ($12): Essential for resealing the housing without pinching the rubber gasket.

Solvent Comparison Table

Solvent Type	Effectiveness on Tar	Safe for Plastic Housing?	Safe for Drinking Water Lines?
Citrus Degreaser (d-Limonene)	High	Yes	Yes (with thorough flushing)
Mineral Spirits	Very High	No (causes micro-cracking)	Absolutely Not
Dish Soap (Dawn)	Very Low	Yes	Yes
Bleach (Sodium Hypochlorite)	Zero (does not dissolve tar)	Yes	Yes (for sanitizing only)

Step-by-Step Removal (4-7 steps)

I'll be honest, this takes elbow grease. Asphalt emulsion cures into a stubborn, rubbery mass that clings to the ridges of your filter sump. Follow these steps exactly to salvage your hardware.

Step 1: Depressurize and Dismantle

Shut the inlet valve on your filter bracket. Open the pressure release button on the top of the housing cap if your model has one. Grab your filter wrench. Turn the sump counter-clockwise. Water will spill out, so keep that 5-gallon bucket positioned perfectly underneath. Lower the sump slowly to avoid splashing contaminated water onto your cabinets.

Step 2: Bag the Contaminated Media

Pull out the black, ruined filter cartridge. Do not attempt to wash it. Drop it directly into a heavy-duty contractor trash bag. Seal the bag tight. The PAHs trapped in the carbon or sediment media are a severe health hazard. Toss it in your outdoor garbage bin immediately.

Step 3: Scrape the Bulk Residue

Take your plastic putty knife. Scrape the inside walls of the filter sump. You'll likely peel off thick, black ribbons of tar. Wipe the knife blade clean with a paper towel after every pass. Throw those paper towels into your sealed trash bag. Get as much of the physical mass out as possible before applying any liquids.

Step 4: Apply the Citrus Solvent

Spray the Zep Citrus Degreaser liberally inside the sump. Coat every inch of the stained plastic. Let it sit for exactly 12 minutes. The d-Limonene needs this time to penetrate the asphalt matrix and soften the bonds. Don't rush this step. If the tar is exceptionally thick, apply a second coat after 6 minutes.

Step 5: Scrub and Rinse

Take your nylon bristle brush. Scrub the interior walls using firm, circular motions. The asphalt should lift away as a dark, oily sludge. Dump the sludge into your bucket. Rinse the sump with the hottest water your tap produces (ideally around 120°F). The heat helps melt the remaining citrus-tar emulsion. Repeat the scrubbing and rinsing until the water runs completely clear.

Step 6: Sanitize the Housing

Asphalt isn't your only enemy here. Bacteria love the oily residue left behind. Mix one tablespoon of unscented household bleach into a gallon of cool water. Pour it into the clean sump. Swirl it around for two minutes to kill any lingering microbes. Dump it out and rinse the housing three more times with clean tap water.

Step 7: Install New Media and Flush

Wipe the O-ring groove dry. Apply a thin bead of Dow Corning Molykote 111 to the rubber O-ring. Insert your new Pentek sediment filter into the cap. Thread the sump back onto the bracket by hand. Tighten it gently with the wrench—don't overtighten, or you'll crack the plastic. Turn the water back on slowly. Open a downstream faucet and let it run for 15 minutes to flush out any microscopic solvent residue.

Alternative Methods (2-3 backup methods)

Sometimes the citrus degreaser isn't enough. If you're dealing with heavily oxidized, rock-hard asphalt that has baked onto the exterior of the housing, you need a different approach. Here are two backup methods I use in extreme cases.

Method 1: Mineral Spirits (Exterior Housings Only)

If the asphalt is stuck to the outside of the filter bracket or the exterior of the sump, mineral spirits work miracles. Dampen a shop rag with Klean-Strip Odorless Mineral Spirits. Rub the stain until it dissolves. Never use this inside the sump. Mineral spirits will cause micro-cracking in polypropylene plastics, leading to catastrophic pressure failures later. Keep it strictly on the outside hardware.

Method 2: WD-40 Specialist Industrial Strength Degreaser

If you can't find Zep, the WD-40 Specialist line (the silver can, not the classic blue and yellow) is a fantastic alternative. It contains a powerful surfactant blend that emulsifies road tar quickly. Spray it on, wait 5 minutes, and wipe away. It's slightly more expensive at around $10 a can, but it rinses cleaner than cheaper automotive tar removers.

Method 3: Professional Hydro-Jetting

If you open your filter housing and find it completely packed solid with asphalt chunks, your problem is much bigger than a stained filter. The contamination is in your main water line. Stop trying to clean it yourself. Call a licensed plumber to hydro-jet your incoming supply line. They will use 3,000 PSI water pressure to blast the tar out of your pipes before it ruins your water heater and appliances.

Prevention Tips

Stopping asphalt from entering your filtration system requires a proactive defense. If you live near newly paved roads or have a shallow well, you are at a higher risk. Here is how I protect my clients' homes from this exact nightmare.

Install a Spin-Down Pre-Filter: Mount a Rusco 100-mesh spin-down separator before your main filter housing. This clear plastic chamber catches large chunks of debris, sand, and tar before they reach your expensive carbon blocks. You can just unscrew the bottom valve and flush the gunk out in seconds.
Check Your Well Cap: If you have a private well, inspect the sanitary seal annually. Driveway sealers and road runoff can easily seep into a cracked well casing. A $40 investment in a new, tight-fitting sanitary well cap prevents surface contaminants from dropping 50 feet down into your water supply.
Verify Municipal Pipe Repairs: When your city notifies you about water main flushing or pipe lining in your neighborhood, bypass your whole-house filtration system. Let the dirty, chemical-heavy water run through an outdoor hose bib for an hour before turning your indoor valves back on. This saves your filters from absorbing the initial shockwave of construction debris.
Use a Backflow Preventer: Install a brass backflow prevention valve on your irrigation system. If your sprinklers pull in asphalt runoff from a freshly sealed driveway, a faulty vacuum breaker will siphon that toxic water straight back into your home's drinking lines.

FAQ

Can I just wash the carbon filter and reuse it?

Absolutely not. Asphalt contains polycyclic aromatic hydrocarbons that permanently bind to the porous surface of activated carbon. Washing it will only release those toxins back into your drinking water at unpredictable rates. You must throw the contaminated media in the trash and install a brand new cartridge.

Will bleach dissolve the asphalt inside my housing?

Bleach is completely useless against petroleum-based stains. Sodium hypochlorite kills bacteria, but it cannot break down the complex hydrocarbon chains found in road tar or driveway sealant. Stick to citrus-based degreasers for the actual stain removal, and save the bleach for your final sanitizing rinse.

How do I know if my well water is permanently contaminated?

You need to order a specialized VOC and PAH water test from a certified lab like National Testing Laboratories. If the asphalt came from a nearby driveway sealing job, the contamination might be an ongoing leaching issue rather than a one-time event. Don't drink the water until your test results come back completely clean.

Why does my water still smell like tar after changing the filter?

The odor is likely trapped in your home's plumbing lines or your water heater tank. Asphalt VOCs easily permeate PEX tubing and rubber bladders inside expansion tanks. You may need to flush your water heater and run a high-concentration hydrogen peroxide shock treatment through your entire plumbing system to neutralize the lingering smell.