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Different Types of RV Holding Tanks


Different Types of RV Holding Tanks
Different Types of RV Holding Tanks

RVs truly are miniature houses, just on wheels, having all the convenience of a stationary building. But for it to be possible to have use of a bath and kitchen facility, you must trade water systems with permanent connections with something with mobility. Your water can’t just travel from and into the ground through stationary pipelines when you’re on the road. In other words, it must come from and leave in different compartments onboard the trailer or motorhome. RV holding tanks are the containers that store the fresh and wastewater in your Recreational Vehicle for this purpose. They hold you over until your fresh water depletes and/or they’re full of wastewater. At that point, you can replenish and dump them out at specific hook-up sites made for RVs. There are three primary varieties used to separate clean water and wastewater. Here are the different types of RV holding tanks outlined and explained.


Fresh Water Tank


As its name makes clear, the freshwater tank is what carries the clean potable water that comes out of your RV’s sink faucets and shower. So long as you maintain it well, this water will be safe to drink. Usually, the freshwater tank is the largest when compared to the other two types of tanks; however, its size can differ dramatically depending on what type of RV you have. A small pop-up trailer or class ‘B’ might only have a freshwater tank with a capacity between 10 to 20 gallons. In contrast, a huge Class A motorhome could have a 100-gallon tank.


Fresh Water Tank Maintenance


To keep the fresh water suited for its intended use, only connect the RV freshwater system to a water supply source using a potable water drinking hose. Made of NSF listed materials for drinking water safety. Typically, this hose is lead free, BPA free, phthalate free and leaves no strong plastic taste in your drinking water. Furthermore, having a water filter in line with the input is essential, most commonly used is a GAC (Granular Activated Carbon) filter. It greatly reduces bad taste, odor, chlorine, and sediment that would otherwise go straight into the tank or line system from the water sources you attach to while at home or traveling. Use of this type of filter will also go a long way in preventing build up and clogging of your kitchen and bath faucets, reducing maintenance and headaches.


You should also be aware of differing water pressure at the different fill or stay and connect sites as well. If the fresh water supply pressure becomes too low due to a specific site hook-up, your showerhead and sinks might only let out a useless trickle while connected directly to the water source and by-passing the holding tank. To overcome this, rely on the holding tank and the onboard water pump to furnish system water. On the other hand, too much pressure can lead to pipe bursting and leaks. Ensure that your RV’s freshwater system PSI is just right by always using an inline water pressure regulator either at home or with a campground’s freshwater outlet whenever you connect to them. Generally speaking, the max water pressure for an RV is 50 PSI for older rigs and 60 PSI for the newer trailers and motorhomes out there, most all city water connections will flow under a minimum 75 PSI.


In addition, when you aren’t actively using your RV, you should either drain out all the water or completely fill the tank, so the air moisture does not encourage contamination. If odors do start developing inside, normal household bleach can sanitize the tank. Mix in one cup for every 15 gallons of water and fill up the tank, letting the solution sit inside for some time. Also run some of this solution mix at the sinks, shower and toilet, enough to smell the Bleach. Then, drain it all out and allow the tank to sit dry for a day. Put more water in at the end of this period and run the lines some and drain it again at the low point drain, repeat this process as needed until you can no longer detect a bleach smell. The tank should be good to go at that point.


Gray Tank


The gray water tank is normally the first of the two receptacles types to receive and collect wastewater. There can be one or more Gray Tanks in your system, they may be also called the Galley Tank. Gray water consists of the drainage from the shower, sinks, and washing machine (if you have one). It’s not fit for use, but it’s also not the filthiest. For the most part, the gray water tank can carry more than a few days’ worth of wastewater depending on occupant’s usage. The more conservative you are with fresh water, the longer you can go before the need to dump. You can minimize usage by not leaving the water just running, using a bowl when washing your face or shaving. Further, outfit your shower with a handheld that has a shut-off valve built in. Take what is commonly called a “military shower” where you turn on the water briefly to wet down, soap up without water, then rinse off with water back on— when dry camping this will save you a lot of both fresh water and waste capacity. This also makes sense even when you’re connected with water and sewer hook-ups at a site free flowing, your hot water heater capacity is normally only around 6 to 8 gallons and has a slow recovery, unlike your 40 to 60-gallon capacity in most stationary homes.


Black Tank


Lastly, you have the dreaded black water tank. This is the one that holds all the sewage and paper from the on-board toilet. This container generally has a maximum capacity that will go longer between dumps than the Gray Tank based on the occupant’s usage. Most RVer’s will minimize toilet usage by taking advantage of restaurant and service station restrooms while traveling, and while in the campgrounds, their common use restrooms and showers. While Traveling, routinely inspect the RV dump valve and check that it is not leaking, and preform maintenance if it becomes difficult to open and close. It is common practice to add clean water and some chemicals by flushing them down the toilet just after they vacate this tank to neutralize the smell and help break down solids, this helps with cleaning the tank while the solution is slushing around when traveling down the road. The only thing worse than having a smelly Black Tank system of your own filling the cabin, is having to smell your campground neighbor’s. Be polite, deodorize!


In terms of the toilet paper you use, you should always opt for RV rated toilet paper that can dissolve easily in the tank. This will prevent clogs in your sewer system and make the dumping of your wastewater more trouble-free. Most Brands only offer a single-ply to further decrease the likelihood of blockages, however some topic dedicated blogs have recommended some 2-ply brands that can also be use.


Waste Tank Maintenance


At some point the time comes for you to get rid of your collected waste, you will need to locate a dump station designated for wastewater at an RV park, campsite, or along the road service center like a truck stop. Use an RV sewer hose (the stinky snake) for this job, tightly connected between the RV’s sanitation center and the dump station receiving portal. We highly recommend that you dump the black tank first so that after you close that gate valve and open the Gray Tank valve, the relatively clean soapy gray water can somewhat wash out the hose. Always disconnect the sewer hose from the RV first, most dump stations, and some RV’s themselves have a freshwater sprayer to provide more water to finish the job of rinsing down clean the interior of the hose into the dump station. Once you have cleaned both in and outside of the hose, stow it away as recommended by our RV’s owner’s manual.


When possible, you should wait until your black water tank is relevantly full before disposing of its contents. This will generate the necessary water pressure for it to flow smoothly and thoroughly out instead of leaving behind lots of remnants in the tank and hose. Most all RV’s Guidelines state that you should vacate both your Grey and Black waste tanks prior to making a trip down the road due to the weight of tank contents, these procedures should be followed. However, a minor amount of waste in either can be acceptable.


In colder freezing temperatures, any or all of these RV holding tanks and associated systems are susceptible to freezing up solid. Even minor freeze-ups can cause a great amount of costly damage and down time, if you’re not using the RV once the weather turns cold, completely vacate all of the holding tanks. Blow out or run RV Anti-freeze through the potable water supply lines and hot water heater. Poor RV anti-freeze down all sink and shower drains, and a little down the toilet. Your RV owner’s packet will have detailed instructions for your unit on how to easily accomplish all of this.


If your plan is to use your RV in Colder Climates, along with many other issues that arise in cold weather, you must have a plan and system in place to protect these water systems from freezing up. Anything that is interior to the cabin is relatively safe since you will be heating your compartment during your use. It’s everything in the “basement” or below the floor that you will want to look at, this area is prone to temperature adjustment that match the outside cold, so any unprotected systems will eventually freeze. All RV holding tanks will require a direct contact electrical heater, commonly known as a Tank Heater, or Tank Pad. Tank Heaters alone are not enough to completely protect your systems, the pipes between the waste tanks and the low point drain valve (dump valve) are the first to fill and if left un-heated will freeze closed. Install Pipe Heaters along all lengths of drain pipes between the discharged portal of the Black and Gray tanks and their respective gate valve. If you are planning on using your RV in some more extreme colder conditions, installing a Gate Valve Heater can be of extra benefit if you have a valve prone to freezing up. Make sure that you understand how and when to turn on this type of heater, they are not used in the same fashion as the other afore mentioned heaters. And don’t forget your fresh water supply lines that run under your floor, this is only ½” (1.27cm) in diameter and is always the first to freeze in cold weather, leaving you with no potable water flow, there are heat panels or heating cables for these too. For information on how to operate all of these type of Heaters, click here.


As you can see, holding tanks and their associated systems are an essential part of your RV and RVing Lifestyle. Using the information laid out here, you can better equip yourself to properly maintain your RV’s water systems and make your road trips free of serious problems as you travel.



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