How To Drain Gray Water Tank On An RV?

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Perhaps you are a new “RVer” and you still don’t have a good understanding of your vehicle’s plumbing system. You are probably confused about how your RV’s water system actually works!

One of the basic things that you ought to know is that most manufactured campers and motorhomes feature a three-tank system that’s responsible for handling both your water as well as waste needs.

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First, there is a freshwater tank whose job is to store cooking, drinking, and bathing water. Second is the black water tank, which is mainly designed for the storage of waste like sewage. And third is the grey water tank, which is designed to store waste-water that wouldn’t normally be stored in the black water tank.  This article will mainly focus on the later, in particular how to drain it and keep it clean.

What is a grey water tank?

Just as mentioned earlier, grey water tanks are basically designed to store waste-water that wouldn’t normally be stored in the black water tank. Such tanks are not necessary for a traditional household as homes are usually connected to a septic tank or the city’s sewerage system. However, mixing black water and grey water in an RV is not practical; one would need a significantly huge tank to contain both wastes.

RV manufacturers have, instead, opted to separate waste like sewage, waste-water produced from showering, waste-water from cleaning the dishes, and even that from the bathroom sink. Greywater is essentially any waste-water that needs disposal that isn’t sewage or human waste.

How to drain your RV’s gray water tank

Draining a grey water tank is quite simple. Just connect a sewer hose to your chosen dump station hole and attach the other end of the hose to your grey water tank valve. Next, open the tank’s valve and let the waste flow. Below are a few useful things to keep in mind with regard to draining your grey tank:

  • Drain your RV’s gray water tank after draining the black water tank. Why? The greywater helps in washing away any residue left behind in the sewer hose from the black water.
  • Do not illegally dump your waste (stealth dumping). Before draining your tank, ensure that you check out the rules and limitations of the state and camping ground where you intend to dump your waste.
  • Scrape your dirty utensils to remove any food or grease before washing and rinsing them. This goes a long way in preventing your RV plumbing from clogging. Food waste is, in fact, mainly responsible for the production of the worst grey tank odors. 
  • Use strainers in your RV’s shower and sink to prevent hair and food from going down the drains.

Where to drain to your RV’s gray water tank

Even though the waste from your grey tank is not as toxic as that from the black tank, it is still considered waste-water, and there are special places designated for dumping such waste. The laws to dumping vary in different states and so it is always advisable to check out the rules and limitations of the location (campground, municipality, state) where you intend to dump your waste. Illegal dumping of waste (stealth dumping) often attracts fines in most locations.

Directly dumping grey water onto the ground is forbidden in most places. Some places, on the other hand, encourage it for the purpose of irrigation.  Below are a few important points to keep in mind:

  • Do not dump your grey water on the pavement. Greywater smells just as bad as black water, particularly that which contains food waste. 
  • Do not contaminate freshwater sources. The nearby lake is not the perfect place for dumping your sink water.
  • Remember to double-check the rules and limitations of the place you choose to dump your waste, and always be considerate of others in that surrounding.
  • Whenever you find yourself at a camping ground that offers dumping facilities, please use them. Draining your gray water just after cleaning some dishes might not seem much, but just imagine how muddy the campground would be if all “RVers” emptied their grey water tanks on the grounds every week.

How to rinse your RV’s gray water tank

It is always a good idea to give a good rinse to the inner walls of your grey water tank after draining the tank. Leaving the walls dirty could cause clogs and unpleasant odors. To clean these inner walls, you will either need a tank rinser or a flush valve. 

Tank rinser

Tank rinsers come already permanently installed on RVs and they provide a convenient means of flushing grease, soap scum, and food residue out of your grey water tank. Tank rinsers have an external hookup for your garden hose and the rinser’s other end is attached into a hole that has been drilled into the rinser’s tank.F Once connected to your hose, the rinser sprays water at very high pressure to thoroughly rinse the tank. 

One aspect to bear in mind when choosing a rinser is its nozzle style. There are rinsers that spray water at 180° (straight streams) while there are those that spray water at a 360° radius. Some nozzles have rotating heads while others remain stationary when spraying.

Flush valve

Apart from allowing you to clean up your grey water tank, this equipment also flushes out your sewer hose, a process that disintegrates any clogs and gets the tank’s sensors clean too. Hook up your garden hose to the equipment’s barrel and then proceed to select either the hose or tank setting in order to direct the water flow where it is needed.

Many flush valves are easy to connect and disconnect with every use and no tools are required to install. There are, however, others that permanently install by connecting to your RV’s outside wall and the tank.

Also included in the flush valve are in-built backflow preventers that ensure your water source is not contaminated. This means that you do not have to stress about the waste-water backing up in your hose. Most flush valves even feature transparent barrels that permit you to see when the flushing water starts running clean.

The best grey water tank treatment techniques

After draining and then meticulously cleaning our grey tank, you could treat the tank for the best results. Note that you don’t have to treat your grey tan each time you drain it; treatment after a second or third draining is enough. Treating your grey tank helps to prevent unpleasant odors and clogs by disintegrating residues like soap scum and grease. 

One important thing to observe is that only the environmentally friendly treatment methods are to be used; employ those methods that are formaldehyde-free and enzyme-based. It is unfortunate that several campground dumping stations are closing because of the use of dangerous tank treatment chemicals by some uncivilized RVers.

Below two kinds of grey tank treatment methods that you should definitely consider using:

Liquid grey tank treatments

Such treatments are chemical-free and constitute bacterial formulas/biodegradable enzymes that make them suitable for disintegrating waste without necessarily introducing toxic chemicals to the surroundings when you drain your grey tank. Just ensure that you are using accurate amounts of the treatment for your grey tank (measuring instructions are on the bottle). 

Also available are liquid sensor cleansers that have been specifically designed to get rid of buildup from your tank’s sensors. In case you notice that the readings from your gauge are not as accurate as before, such cleansers will help eradicate any buildups left behind and considerably improve your tank’s readings.

Drop-in grey tank treatments

Such treatments include pouches, scoopable additives, and tablets. A lot of RVers actually prefer this type of treatment over liquid tank treatments mainly because of convenience. Unlike liquid treatments, drop-ins do not require measuring. In addition, with drop-in treatments, you do not have to worry about any accidental spillages.

How often should I drain my RV’s gray water tank?

If you live in your RV, I would recommend cleaning your tank once per year. If you rarely use your rig, I would recommend cleaning and flushing your grey tank before putting your RV into long-term storage. Part-time RVers are, however, advised to clean their tanks after every use.

Signs that your gray tank needs replacement

The most obvious sign that your grey tank needs repair or replacement is if you notice any leakage. Other than leakage, you also need to monitor the seams of your grey tank. If they or worn out or cracked then a replacement is definitely needed.

All in all, draining your grey tank and keeping it clean will go a long way in maintaining the proper functioning state of your tank. Remember to drain your tank at the right time and most importantly at the right place.

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