RV Guide: Blackwater vs Greywater Tanks

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Managing wastewater can be one of the most stressful aspects of RVing for first timers. Where do you do it? How often should you dump? What equipment will you need? Also — it’s gross, right? The list of questions and the odious nature of the task can be overwhelming on your first trip. But it really shouldn’t be! It’s actually fairly easy to do, and we’ve got a few easy tips to help you keep it as clean as possible.
Gloves giving two thumbs up

Greywater vs. Blackwater

First, some basic definitions. Your RV will typically have two wastewater holding tanks. The greywater tank is where your sink and shower will drain to. The blackwater tank is where the toilet contents go. There are some variations depending on your unit, such as having two greywater tanks or draining the shower to the blackwater tank. But the fundamentals are the same. 

Drain Your Tanks

When draining your tank at a dump station, you want to drain your blackwater tank first. This is so that when you drain your greywater, it will help to clean out any lingering debris from your hose. First, make sure the valve on your outlet is closed, so it doesn't dump on you when you uncap it. Slowly remove the cap from your black tank outlet and attach your hose by twisting it in place. The end you want to hook up to your tank has hooks around the edge to hold it in place, so it should be easy to determine which end to connect to your RV. Stick the other end into the waste station, make sure the connection is tight on both ends, and then release the valve on the RV outlet. It is a good idea to flush your blackwater tank as you are dumping to help move any debris through and there should be a hose at the waste station you can use to do this.

After dumping your blackwater tank, you can move on to your greywater tank. Some RVs will have a separate outlet for greywater. Others have one outlet, but with separate valves. If you are unsure, refer to your owners manual or inquire with your renter. Either way, be absolutely sure to CLOSE ALL VALVES before removing the hose. You don't want any remaining sewage debris to make an encore appearance after the show is over.

Tip: Don’t empty your blackwater until it’s close to full. It may be tempting to empty your blackwater as often as possible, but this is a mistake. Having a lot of water in the tank helps to push everything out and keeps your hose clear of blockage. Additionally, letting the water sit for a while will help the solids break down. If you empty your tank too frequently, it’s likely that some solid waste will remain unflushed and get backed up down the line. 

The general rule is to empty your tank at two-thirds full. This gives you a happy medium between not getting too full, but also having enough water to prevent clogging. However, you shouldn’t be afraid to empty a tank at half full if it’s more convenient. A lighter load means better fuel economy, so use your judgement on when the best time to dump is.

Keep Your Gear in an Outdoor Bin

RV maintenance hatch

You want to keep all your sewage gear separate from all other tools and supplies. If your RV has a compartment on the outside, that’s the perfect place to store all your dumping gear. If your RV is a trailer, you can keep it in the truck bed. You may have to get creative to find a good place, but it’s ideal to never have to bring it inside of your RV to avoid any cross contamination or foul odors.

Limit How Much Food Waste You Put into Your Grey Tank

While it's certainly acceptable to use your sink for cleaning dishes (that's what it's there for, after all), too much food waste can add up and result in a foul smell from your drains. To avoid this, consider how much waste you're sending down the drain. 

As an alternative, you can put a tub in your sink when washing particularly dirty dishes. Then when you are done, just dump the tub outside. If you’re rinsing out empty cans, you can use a water hose outside instead of doing it in the sink. The leftover juices from canned beans can be especially odorous.

What You’ll Need

If you’re renting an RV, some of this equipment may be included. Be sure to check with the owner so you know exactly what you need to bring.

Disposable gloves: Make sure you’ve got plenty of these on hand. You don't want to handle this stuff with your bare hands! Some people like to use reusable gloves. While that's an option, it's less sanitary and is one more thing you'll have to worry about keeping clean. 

Sewer hose and connector: A good quality sewer hose is an absolute must. If you get a poorly made hose, it's only a matter of time before it springs a leak. That's not a situation you ever want to find yourself in. The Camco 20’ kit we have here is very good quality for the price and it comes with a 4-in-1 adapter so it can fit to any waste station. The clear elbow adaptor is especially nice, since you can see what's passing through your line in case there's a problem.  

Sewer hose support: This holds your hose at an angle to help gravity do its job and keep the juices flowing while you're dumping. This will help keep your hose from clogging and getting backed up. It will also keep your hose off the ground, which will keep it from getting covered with dirt and mud, which is just a nice bonus. This is also a necessity because some RV parks require you to use one of these.

Septic safe toilet paper: It’s not a good idea to flush just any old toilet paper into your septic tank. Regular toilet paper doesn’t break down quickly enough and can lead to clogging. Septic-safe toilet paper will break down faster and with less water. 

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