DWV Common Problems and How to Solve Them

If you’re a homeowner or run a business, you rely on your plumbing to work smoothly daily. But sometimes, your Drain-Waste-Vent (DWV) system can throw a spanner in the works. At All Needs Plumbing, we’ve seen plenty of DWV common problems over the years, and I want to share some insights to help you spot issues early and understand why professional help is the best way forward.

What Is a DWV System?

Your DWV system is the backbone of your plumbing. It drains wastewater from your sinks, toilets, showers, and appliances, and vents air through pipes that extend above your roof. This venting prevents pressure build-up and stops sewer gases from entering your home. When everything works well, you don’t even notice the system. Things that go wrong, like drains that take too long to clear or water damage, can be very annoying.

DWV Common Problems You Might Face

Blocked or Clogged Drains

Blockages are the most common DWV problem we fix. Pipes can get clogged with cooking grease, shower hair, food scraps, soap scum, and even tree roots. When this happens, water drains slowly or not at all. You might hear gurgling noises as air struggles to move through the pipes. Sometimes, foul odours escape from your drains.

These blockages often start small but grow quickly. If ignored, they can cause backups that damage your flooring and walls. The tricky part is that blockages can happen anywhere in your system - from the trap under your sink to the main sewer line.

Venting Issues

Your DWV vents let air in and sewer gases out. Air can't flow properly if a vent pipe gets blocked by leaves, debris, or even a bird’s nest. This causes your drains to slow down and sometimes gurgle. You might even smell sewer gas inside your home, which is unpleasant and unhealthy.

Venting problems often go unnoticed until they cause noticeable symptoms. Because vents are usually on your roof or in hard-to-reach places, it’s best to have a professional inspect and clear them.

Pipe Leaks and Cracks

Pipes can develop leaks or cracks due to corrosion, shifting soil, or poor installation. Leaks often appear as damp patches on walls or ceilings, mould growth, or a musty smell. Sometimes water damage occurs long before you notice the leak itself.

Fixing leaks can be costly and time-consuming. A professional plumber can detect leaks early and use specialised equipment to repair or replace damaged pipes.

Improper Pipe Slope or Sagging

DWV pipes rely on gravity to move waste. If pipes sag or don’t have the proper slope, water and waste can pool inside, causing blockages and bad smells. The minimum slope for most DWV pipes is 1/4 inch per foot (about 2%). This slope helps waste flow smoothly without getting stuck.

Sagging pipes often happen because of poor support or ground movement. Fixing this involves adjusting pipe angles and adding supports to keep pipes stable.

Frozen Pipes

In colder parts of Australia, pipes exposed to freezing temperatures can freeze and burst. When they freeze, no more water flows through them, and the pressure inside them can crack or burst, causing flooding and damage.

If you live in a colder area, insulating your pipes and keeping your home warm can help prevent freezing. But if pipes freeze or burst, call a plumber immediately to avoid significant damage.

Pro-Tip: Pour boiling water down your kitchen sink weekly to dissolve grease buildup before it hardens. This simple step can prevent many common kitchen drain blockages.

Troubleshooting DWV Problems

When you notice slow drains, gurgling sounds, or foul smells, it’s time to act. Here’s how we approach it:

Diagnose blockages

We start by visually inspecting the affected drains and pipes. We use specialised cameras to look inside pipes and find where the blockage is without digging or guesswork, saving time and money.

Clear blockages

We use mechanical tools like drain snakes or augers to break up or pull out the clog depending on the blockage. We use hydro jetting for tougher blockages, a high-pressure water blast that cleans pipes thoroughly without damaging them.

Inspect vents

We check vent pipes on your roof for debris, nests, or damage. Clearing these blockages restores proper airflow and stops sewer gases from entering your home. If vents are damaged, we repair or replace them.

Fix leaks

We locate leaks using moisture meters or thermal cameras. Small cracks can be patched with sealants or clamps, but often, replacing the damaged pipe section is the best long-term solution.

Check pipe slopes

We measure the slope of your DWV pipes and adjust them if needed. Adding pipe hangers and supports prevents sagging and keeps waste flowing smoothly.

Pro-Tip: Avoid harsh chemical drain cleaners. They might clear a clog temporarily, but they can eat away at your pipes over time. Instead, try flushing your drains with a mixture of baking soda followed by vinegar. Spray it on and wait 15 minutes. After that, wash it off with hot water. This can help keep minor blockages at bay, but don’t rely on it for serious clogs.

When Should You Call Us?

If you hear gurgling noises, smell sewer odours, or have slow drains that don’t improve, don’t wait. These are signs of serious DWV problems that need expert attention. We’ve been fixing these issues for years across St George and Sutherland Shire, and trust me, DIY fixes often worsen things. Calling us early can save you time, money, and stress.

FAQs About DWV Common Problems

How do you test a DWV system?

We test DWV systems using a few methods. A water test involves filling the pipes with water to check for leaks. Smoke tests push smoke through the system to find cracks or vent blockages. Air pressure tests check if the system holds pressure without leaks. These tests are essential during installation and troubleshooting to ensure your system works properly.

What is the difference between DWV and stormwater pipe?

DWV pipes carry wastewater and air ventilation from your home’s plumbing fixtures. Stormwater pipes, conversely, carry rainwater runoff away from your property. They are usually bigger, made from different materials, and installed separately because they handle large volumes of water during rain.

How much pressure can DWV PVC take?

DWV PVC pipes are designed for gravity flow and low pressure. They aren’t built to withstand the high pressure in water supply pipes, and using DWV PVC for pressurised water lines can cause failures.

What is the minimum slope for DWV pipe?

The minimum slope for DWV pipes is generally 1/4 inch per foot (about 2%) for pipes 2 1/2 inches or smaller. Larger pipes may require a slightly lower slope. This slope ensures waste flows smoothly and prevents blockages.

Can you mix DWV and PVC?

Yes, DWV systems often use PVC pipes. Compatible fittings and adhesives are essential when mixing PVC with other materials to ensure a secure, leak-free connection. Incorrect mixing can lead to leaks or system failure.

What if I want to know more about DWV common problems?

Don't hesitate to reach out if you want to learn more or suspect your DWV system has issues. At All Needs Plumbing, we offer a $0 callout fee, 24/7 same-day service, and a 15% seniors’ discount because we believe everyone deserves reliable plumbing. 

In addition, we'll give you $150 off if you decide to upgrade your hot water system. We’ve helped countless homeowners and businesses in your area keep their plumbing running smoothly. Let us take the stress off your hands and fix your DWV problems quickly and professionally.

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