Fresh Water Tank Care

Fresh water tanks normally require little maintenance, unless you live in an area with freezing temperatures and have to winterize your water system or you fill them with contaminated water.  You will want to flush and possibly sanitize your fresh water tanks after a season of storage or after contamination.  Whether you leave them full, drain them, or winterize them, you may still want to flush and sanitize them before setting out again each year after they've been sitting all winter.  Algae sometimes grows in full tanks and dust, insects, and mildew might accumulate in empty or near empty ones.  You will want to clean out the antifreeze used for winterizing.   It isn't toxic, but it does make the water look, smell, feel, and taste funny.  In any case, flushing and sanitizing takes care of the problem.   If you live where you don't have freezing temperatures, I suggest you store your RV with the fresh water tank full.   That way it is ready if you need or want to use it and, at least in my experience, a full tank doesn't get stagnant as quickly as a partially full one.  Most of the organisms that might foul the water need air so a full tank limits growth by limiting air.

Avoid putting contaminated water into your fresh water tank.   Always fill your tank from a source that is known to be acceptable drinking water quality.  If there is any question, use an appropriate in-line filter.  If you should put contaminated water into your fresh water tank, such as from an unprotected well or spring, flush and sanitize the system as soon as possible to remove any potential micro-organisms and other contaminants.  City water supplies are usually treated to be pretty safe and usually contains enough residual chlorine to protect the water in your tank, but untreated water from private wells or springs may not be.  You might not know if water from a campground is safe or not.  It should be, but an unreported or undetected problem could come up without warning.  If you find your water shows any unusual characteristics, such as being cloudy, muddy, or smelly, it may be contaminated.  You could take sample and have it tested or just empty, sanitize and refill your system from a known safe source.  Always use a hose rated for potable water to fill your fresh water tank.  Ordinary garden hoses may introduce a plastic taste and even toxic chemicals into your water.  NEVER use the same hose you use to rinse your sewer drain hose to fill your fresh water tank!  Doing so is a sure way to contaminate your fresh water with traces of sewage!  I don't know about you, but I sure don't want to drink or wash my hands and face let alone drink water that has even a trace of sewage in it!

Sanitizing a fresh water tank consists of two major steps.   First completely drain the tanks, then use a diluted solution of ordinary household bleach and water to kill any bacteria and remove any stagnant odors.  I've seen recommendations anywhere from 1 teaspoon per 100 gallons up to 1/4 cup of bleach for each 15 gallons of tank capacity.   An easy formula to remember is to add 1 cup of plain, unscented chlorine bleach to 1 gallon of water.   Add the solution to your fresh water tank and fill it.   Drive around a little to mix the solution and clean all the surfaces inside the tank.  Pump it through the lines to all the fixtures.  You should be able to detect a light bleach odor at each fixture.  Then let it sit over night for best results.  Lower concentrations are easier to flush out without leaving a nasty residue.   Higher concentrations will be more reliable at killing offensive bacteria but don't go overboard on the bleach.  The residue left when you empty a bottle of bleach is sufficient to treat a gallon of water, so it doesn't take a lot to sanitize your RV system.  Fill the tank.   Turn on the pump and let water run from each faucet until you can smell the bleach at each one.   If your solution is too weak to smell you may need to add some more bleach.  Driving the unit a few miles will help mix the solution and clean the walls of the tank.  Let it stand for at least 3 or 4 hours.  Overnight is even better.  Drain the diluted bleach solution and flush the tank with clean water.  To ensure there is no bleach residue, fill the tank again with clean water and baking soda.  Mix a 1/2 cup of baking soda in a gallon water, add it to a nearly full tank or, better yet, put it into an empty tank and fill it up.  Drive around a bit to make sure the solution is thoroughly mixed and all the interior surfaces flushed.  Run water through each faucet until the chlorine smell is gone to clean the plumbing.  Driving around a bit will help make sure it reaches all interior surfaces (like to top!) of the tank.  Drain the soda solution and re-fill and flush the tank with fresh water.  If you have any concerns about the water quality you can drain the tank and refill and flush it again with clear water to be sure the soda solution has been thoroughly flushed out. Be sure to drain and flush your hot water heater as well as the fresh water tank, lines, pump, and fixtures.  When you are satisfied that the water coming out of your faucets is acceptable, drain the tank one more time and refill it with fresh water, just to be sure you've gotten rid of all the bleach and soda.

Filling your fresh water tank.  Always fill your fresh water tank from a safe source.  If you have any questions or concerns about sediment or hard water, be sure to use an in-line filter when filling your fresh water tank.  The faucets at dump stations are often contaminated by sewage, so avoid using them to fill your tank.   Most RVs have a gravity fill where you can insert a garden hose or dump in fresh water from containers to fill your tank.  Some older campers and trailers have a pressurized water system that is filled by connecting a hose to a female fitting on the unit.  Filling the tank compresses air in the tank to provide pressure to deliver water to fixtures.  Some units only have a city water connection and use a "Transfer" or "Fill" switch or valve to divert water to fill the tank.   Either way, ALWAYS use a clean, potable water rated hose to fill your fresh water tank.  They are usually white or light blue.  Keep a separate hose of a different color (ordinary garden hose) for rinsing your dump hoses and flushing your holding tanks so they don't get mixed up.  Different colors shouldn't be a problem.  Most potable water hoses are white or light gray with a blue stripe or are light blue.   The most common color for garden hoses is green.  At any rate DO NOT use a hose to fill your fresh water tanks or jugs that has been used to rinse sewer hoses and never use your fresh water hose to rinse sewer hoses.   Just the thought of the contamination that might be transferred into the fresh water supply is enough to make me want to throw up!  A fill attachment for your fill hose will make it easier.  It looks like a short piece of hose, usually clear plastic, with a female hose fitting on one end to connect to your hose.  The other end has no fitting and is usually cut at an angle.  There is usually a shutoff valve on the fitting end.  If not, you can get one at an RV store, hardware store or home and garden center. The open end of the hose is pushed down into the fill port on your RV so you don't have to stand there and hold the hose.  Make sure the filler tube is clean.  When sanitizing a tank with a gravity fill you can usually just dump the bleach or the soda solution into the fill port before adding water.  If your RV doesn't have a gravity fill, sanitizing the fresh water tank will be a little more difficult.   Some folks just use a funnel to fill the fresh water hose with bleach and then hook it up to the faucet to push it through and get it into the tank.  Others prefer a device that siphons the bleach or soda solution from a jug and mixes it with the water as you fill the tank.  These gadgets are typically used to apply lawn and garden fertilizer so you'll probably have to buy them at nurseries or home and garden centers.  Buy one especially for sanitizing your tanks and never use it for applying fertilizer.  Some RVs have design limitations that force the plumbing from the gravity fill port to the fresh water tank to lack sufficient slope for water to flow easily.  If you get a lot of water spilling back out around the hose when filling the tank, this may be your problem.  You may be able to solve it by raising that side of the RV using leveling jacks or leveling blocks.  Another solution that sometimes works is to cut a piece of potable water hose long enough to reach through the filler tube all the way to the tank so you can deliver water directly into the tank.  Cut the piece to preserve the female hose fitting so you can connect it to your regular filler hose.  There should be a vent tube from the tank back to the gravity fill fixture.  Be sure to remove the plug from the vent line so air can escape from the tank as it fills.  If you fail to remove the plug or the vent tube is somehow kinked or blocked air will bubble back through the gravity fill port itself, interrupting the flow of water into the tank.

Fresh water tanks usually don't require any chemical treatments like waste water holding tanks always do but if your water supply is tainted or your tank develops offensive odors, there are products you can get from your RV store to freshen your fresh water tanks such as TastePURE Drinking Water Freshener.   DO NOT use holding tank chemicals in your fresh water tank. They are toxic!  Unless your water begins to smell or taste bad, it probably doesn't need to be treated or flushed and sanitized. If your water supply has lots of minerals in it, you may want to use a filter attached to the hose when filling your tanks or connecting to city water or add an internal filter to your system.  Filtering out minerals and other particles will help keep your fresh water fresh and avoid buildup of junk in your hot water heater, fresh water tank, plumbing, and fixtures.  Most city water supplies contain enough chlorine to keep your fresh water tank safe from bacteria but it may still need to be filtered.   If you fill your tank with untreated well water, you may need to add a small amount of bleach to discourage bacteria growth. A little bleach added each time you fill the tank will help control bacteria growth. If you can smell chlorine at the fixtures, you've put in too much ! Just the residue in a gallon bleach jug after its been emptied is enough to protect a gallon of water if you fill it for storage so it doesn't take a lot to protect a even a full tank of water -- just a few drops per gallon. A tablespoon full should be enough for a 100 gallon tank.

By the way, if you get a bad odor when you turn on a faucet, be sure it is coming from the faucet and is not wafting up from the drain.  I have seen situations where it seemed like the water smelled bad, but it was really just odors in the drain being activated and atomized by water going down the drain.  Sometimes if odors are coming up from a sink drain you only need to run a little water into the drain to fill the P-trap to block odors from the holding tank. Odors from sink drains may also be caused by a stuck or damaged  in-line or cheater vent.  They are usually located under the sink to allow the drain to flow freely when it malfunctions the sink may drain slowly and it can allow odors from the tank to come back up into the RV.

A quick way to check to see if the fresh water tank is actually smelly, is to open the drain valve on the fresh water tank and check the water there.  If it is OK, the problem isn't in the fresh water tank.  But, even if the water in the tank isn't bad, water in the lines or hot water heater may be.  Try running each offending faucet for several minutes with the city water hooked up to flush the lines.  

Another common source of fresh water odors is the hot water heater.  If the odor is only detected or is stronger when the hot water faucet is turned on, the problem is probably the hot water tank.  Warm temperatures create biological and chemical reactions that sometimes result in unpleasant odors, especially if there is any residual antifreeze left in the tank.  Shut off the water heater.  Then connect a hose to your city water inlet and open the drain on the hot water tank.  You'll probably smell bad water for 10-15 minutes before the tank has been cleared of odor causing materials.  Organics in water or left over antifreeze can turn foul from heating the water.  You shouldn't have any problems if you you properly flush the hot water heater and sanitize your fresh water system at the beginning of the season.  If simply flushing the hot water heater doesn't cure the problem you will need to sanitize it using a bleach solution to mitigate any residual odor causing materials.  You may want to follow it by rinsing it with a mixture of baking soda and water to clear away the bleach smell and finish freshening the tank.  While you're at it, check the condition of the anode rod on the drain plug.  These are designed to sacrificial.  That is, to be used up as they protect the exposed steel of the tank.  If there is less than 25% remaining, they need to be replaced.

Hoses for filling your fresh water tank.  You should only use hoses designated for drinking water or potable water to fill you fresh water tank or connect your RV to city water.  Ordinary garden hoses may leach a plastic taste and possibly toxic chemicals into the water.  Potable water hoses are made from compounds that won't contaminate your water supply and some have anti-microbial additives to help prevent grown of mold or mildew.  They are also reinforced to withstand the constant pressure of being used for a city water connection.  Potable water hoses are usually white with a blue stripe or light blue with a white stripe. The packaging will clearly identify it for use for "potable water" or "drinking water", but once it has been removed from the package, the only identifier is the color, which is usually sufficient for owners to tell their drinking water hose(s) from other hoses.   Also NEVER NEVER NEVER use the same hose to fill your fresh water tank and to rinse your dump hose.   Never fill your fresh water tank from the faucet at dump station that is used to rinse sewer hoses.   Even if the water is clean and potable, the chance of the connection being contaminated by dirty hands handling sewer hoses or bad stuff being siphoned back up into the fixture is too great and you may risk getting sick.  Just the thought of ingesting sewage is enough to turn my stomach!   Try to drain all the water out of the hose before storing it back in your RV.  Use end caps or connect the two ends together to prevent bugs from taking up residence in your hose while it is in storage.  Be especially sure your hose is drained before you put your RV into winter storage if you live where you get freezing temperatures.  Water remaining in the hose will freeze and is likely to burst the hose.  When you get out your hose to fill your tanks or connect to campground hookups, connect the faucet end first, turn on the faucet, and let a little water run through to make sure it is clear of any debris or stagnant water before filling the fresh water tank or connecting to the city water connection on the RV.

A quick fill pigtail is a handy accessory for filling gravity fill fresh water tanks.  This consists of a short piece of potable water hose with a female fitting and a shutoff on one end and the other end usually cut at an angle.  Very often the hose is clear so you can watch water flowing through it as you fill the tank.    It goes about a foot down into the fill port and keeps the hose from falling out while filling.  The shutoff lets you turn it off quickly when the tank is full and water begins to overflow.  If you have trouble with water coming back out of the fill opening before the tank is full, you might try making a longer pigtail, one long enough to reach down into the tank.  You  may have to buy a short potable water hose and cut off the male end.

As briefly mentioned above, water filters are often a good idea.  You can get a filter that connects in-line in the hose to filter water that is going either into your fresh water tanks or into the city water connection.  Another convenient way to filter your water is to install a permanent filter so that both water pumped from the fresh water tank and water coming from the city water connection goes through the filter.   That way you always have clean water at your fixtures.   Specialized RV water filters are available at RV supply stores but many RVers have had good luck adapting residential filters and claim they are less expensive.  You can make up connections to put a large residential style filter in line  in your hose to filter water as you fill your tank or deliver water to your city water connection.  You may need some kind of crate or stand to protect it from tipping over and it would be a good idea to place it next to the campground pedestal or under your RV so it doesn't become a trip hazard.

Monitoring fresh water levels is usually done via a monitor panel that displays the status of many on board resources.  Most monitor panels include functions for fresh water, gray water, black water, battery, and propane.   Most of these systems use sensors installed through the wall of the tanks to measure the amount of liquid in the thank.  Sensors in fresh water tanks are less likely to become contaminated and fail or give false readings than those in holding tanks, but hard water deposits can eventually fowl them.  They can be difficult and expensive to repair or replace.  I recently read a review of new monitoring system that uses inductive panels installed on the outside of holding tanks to replace faulty sensors and improve the accuracy and reliability of tank readings.  It is called See Level II and retails for around $235.  Installation is fairly simple if you have access to the side of your tanks.  In a normal installation you would install the new sensor panels near the existing sensors connect them to the old wires.  Then you connect the new panel to the other end of the wires at the original monitor panel.  Other techniques for measuring how much fresh water you have in your tank includes a visual inspection of the tank (if you have access to it) or a siphon based gauge that gives you an external visual representation of the water level by sticking a tube down into the gravity fill and viewing the water level in a tube on the outside of the RV.  To do this you need clear tubing long enough to push all the way to the bottom of the tank, then loop outside down at least to the bottom of the tank, then back up above the top of the the tank.   Since water seeks its own level, the tube should fill to the level of water in the the tank.  If your monitoring panel fails to work, first check all the connections and any related fuses.  Then try to clean the sensors in he tanks.  One easy and safe way to clean a fresh water tank without introducing unsavory chemicals is to put some ice in the tank, then fill it about half way, and drive around a bit.  The ice will scour deposits from the inside of the tank (hopefully including the sensors) and will then melt so you can drain it out.  You will want to thoroughly drain and flush the tank before refilling it with fresh water to eliminate any residue the ice scraped from the tank.

If you don't have an electronic measuring system to check how much water is in the tank you can sometimes view the side of the tank to get an idea.  Lacking access you may be able to fabricate an external gauge from clear plastic tubing.  Insert it into the gravity fill hole far enough to reach to the bottom of the tank and then siphon water out of the tank to fill the tube.  Allow the tubing to hang down at least to the bottom of the tank and lift the open end of the tube above the filler, leaving a loop to the bottom of the tank.  You should then be able to see the water level in the tube.  I installed a light behind the translucent water tank in my enclosed motorcycle trailer, then cut a slot in the front of the paneling in front of the tank so I could easily view the water level whenever I turned on the light.  I used a momentary contact switch so I don't accidentally leave the light on and drain the battery.

Fresh water odors.   Occasionally fresh water systems will develop unpleasant odors.  Sometimes you may get a bleach smell if you've sanitized the system and haven't flushed it adequately.  Fresh water can stagnate if left unused for a long time.  It may begin to host algae or mildew, giving the water a nasty taste.  If you get bad smelling water at a faucet, try opening the drain valve on the fresh water tank and check the water there before flushing the whole system.  I've seen cases where it appeared the water was bad but what was really happening was the water activated nasty odors in the sink drain.  Simply flushing the drain with a bleach solution solved the problem.  The hot water heater is another common source of odors.  The warm water is sometimes an ideal home for microbes that can make your water stink and taste bad.  Fresh water normally doesn't require any special additives.  If you use city water, the water you fill the tank with will already contain a certain amount of chlorine that should protect it against algae etc.  If you fill it from an untreated source, such as a well or spring, you may need to add a bit of bleach to protect it.  It doesn't take much.  The residual bleach in an empty 1 gallon bottle is enough to treat a gallon of water.  I wouldn't use more than about 1/4 cup for an 90-100 gallon water tank, often a tablespoonful is sufficient.  If you get a bleach smell when you turn on a faucet, you've used too much and will need to drain the tank and refill it.  If you have chronic problems with smelly water there are commercial fresh water treatments available most places RV supplies are sold, but I would only use them as a last resort.  Sanitizing and thoroughly flushing fresh water systems are usually all that is needed.

Damaged tanks can be difficult to repair.   They are often made of LDPE plastic, which is highly resistant to solvents and, therefore, cannot be easily patched using solvent based sealants.  LDPE can be welded using plastic welding techniques.  Fortunately fresh water tanks are usually well protected and, unless you allow them to freeze and split, seldom crack.  Unlike waste holding tanks, they are usually not an irregular shape and a tank of similar size and shape can often be found to replace them.  In addition to size and shape the position and style of openings or connections will also be a major concern.  There are usually at least three plumbing connections:  inlet, outlet to the pump, and drain.  Some may also have an overflow port. If you have or want to add a monitor system you will need to install sensors on the tank.  Old style sensors require drilling to install them through the wall of the tank but there are also sensor panels that are glued to the outside for either new installations or to replace failing sensors on existing tanks.

Drink up!