Fresh Water Tank While Towing.

[Peto]

What is the best practice. Tow empty or full or with just a few gallons?

So far we have been camping at sites with no water hook ups but clean water available near by to fill up. I've towed completely empty and completely full and feel no difference (plenty of truck).

I have also towed with about 10 gallons (total SWAG) in the tank just in case we experience an issue and need to make an unexpected overnight stay.


Getting ready for a long trip (12 nights out) with a combination of full hook ups and boon docking.

Plan is to tow empty (10 gallons ish) if the next stop is full hook ups and fill full if next stop is a boondock.

Is it the weight, the sloshing or a combination of both that make this a question?

 

[Summit Pond]

We've done all three: full, empty and partially. Theoretically you should be able to tow with a full load of water, but there have been instances reported in the forum of tank issues due to insufficient mounting and the added weight.

What we normally do is fill with about 10 gallons (again, an estimate based on time and the wonderful idiot light meter) and carry a few extra gallons in old plastic milk jugs (stored in the shower) to use if needed for flushing the toilet in an emergency. We always have several gallons of potable water in jugs that we reuse for drinking; the tank water is for doing dishes, brushing teeth, showers and flushing the toilet.

 

[flybouy]

We don't boondock but I do travel with ~20 gl of freshwater in the tank. The FW tank in our unit is in the front so it can effect the hitch wt but that's not the primary reason for not filling the tank. The water in the tank is used when we stop and use the toilet at a rest stop and for when we start setting up at a cg. While I'm setting up we can get get water for the dog, wash our hands, etc. We also use the water when breaking camp for flushing the toilet & washing hands before hitting the road.

Why only a partial tank? Typically we don't use enough water to exchange the water to justify a full tank. I don't like to keep water for an extended time, especially in hot temperatures during the summer months. This is what works for us. Only you know, or will find out, what works best for you.

 

[fjr vfr]

Everyone has a different opinion on the subject. I have been dragging my 5th wheel all over the country for about 7 years now and always have tanks full. Never an issue.
The only exception is traveling during winter when trailer is winterized.
During those times we keep bottles of drinking water in the trailer. I keep several plastic jugs near the toilet half pink antifreeze and half water. We use them when we need to use the toilet during the night.
You will get many different opinion's though.

 

[NH_Bulldog]

Similar to others above, when we are traveling we typically always have 10-12 gallons in the fresh tank for bathroom breaks, hand washing and water for the dogs. Most places we have boondocked have a water fill at the entrance so we fill up when we arrive. We also carry a 6-gallon water jug since we have a gravity fill and can add water any time we get low. If we were truly going to be off grid with no water source at our destination, we would fill the tank before we hit the road (or I would pay a professional courtesy visit to the nearest local Fire Department and ask if I can fill up there). Ours is in the back, so at most, it takes some weight off the pin, but is really unnoticeable.

 

[jasin1]

I usually travel with a small amount of water for liquid only bathroom breaks… Wife’s cousin had a tank failure from traveling with full tanks on his toy hauler

I think a half a tank may be worse ….a lot of weight sloshing around stressing the flimsy silicone covered connections hastily put together in the factory but i guess you would hear about more failures if it was really an issue….wonder if half tanks can contribute to trailer sway?…..like having a person run back and forth or side to side in the trailer while towing

 

[jxnbbl]

Fill her up....


The way we travel we need water for 3-4 days between campgrounds and make full use of the trailer. After reading the entries in this forum I do recommend filling to the brim and taking a good long test drive before making that first 2000 mile trip to ensure there are no leaks as well as the usual camp in the driveway to work out the kinks.

 

[Raptor Dave]

I'm sure everyone has their own system.
Like others....we keep enough in the fresh tank for toilet use and washing hands when traveling. Looking ahead at the schedule and seeing what and where we're going end up will dictate if I stop and filler up for our necessary needs.
It just doesn't make sense to me to be hauling an additional 8.34 lbs per gal of weight around unnecessarily. ie...75 x 8.34=625 lbs of additional weight all day long unless that might be the last stop we can fill up before going into the woods for 3-4 days.
We have 104 gal fresh tank so we're usually good for a couple days of just hauling 20-25 gals around.
To each their own I suppose.

 

[JRTJH]

Here's a consideration I haven't seen yet:

Before making the decision of full, empty or partially full, owners really ought to understand their water tank. Years ago, water tanks had baffles in them that reduced "water splashing" or "water movement" inside the tank. Those baffles more or less kept water "still inside the tank"... Back then, it really didn't matter much whether you towed with a partially empty tank or not because there was limited water movement inside the tank.

Those "molded in baffles" took up space inside the tank which reduced capacity or meant a larger tank to carry the same amount of water. As manufacturers started building smaller, ultra-lite trailers led to the need for lighter tanks that carried the same or more water than before, so the baffles started to get smaller or they were eliminated completely. Thats when people towing with half empty tanks started noticing increased sway in some rigs, they also started having "tank problems" like broken straps, tanks falling out of position and split/ruptured tank walls...

Why? A 45 gallon water tank carries about 350 pounds of water (more or less). If the tank is full, that water is essentially "static even when the trailer is moving. But, a half full tank with no baffles, has about 175 pounds of water, swaying back and forth as the trailer moves down the highway. Increase sway, you increase water movement. Sooner or later, you get to a point where you have 175 pounds of weight "slamming against the tank walls" and changing the "balance of the trailer"...

If the tank is in the front of the trailer, there's less movement and the sway is not as noticeable. Same with tanks positioned above the axles. That "slamming back and forth" is not as noticeable and trailer sway isn't greatly affected. On the other hand, if the tank is located in the rear of the trailer, that sloshing is increased. Depending on the rig (tow vehicle, hitch sway control, cargo loading) sway can be "not noticed" or can make a trailer "**** to control on the highway"...

Why? sway induced inside a half full water tank with n o baffles. A few years ago, we had many more reports of broken tank straps, damaged tanks, etc. Keystone didn't start using baffled tanks again, they just changed the mounting system to keep the tanks in position better. We still have "175 pounds of water slamming into the tank ends when we tow with a half full tank"...

Some rigs, depending on how they're set up, will notice that weight in handling difficulty, some better matched tow vehicle/trailer combinations won't notice increased sway at all... But, if you tow "half full" with a tank that doesn't have baffles, you will have an increased possibility of water movement that could damage your tank installation or the tank itself.

How to eliminate that water movement? Tow with a full tank or with an empty tank.

 

[Raptor Dave]

Here's a consideration I haven't seen yet:

Before making the decision of full, empty or partially full, owners really ought to understand their water tank. Years ago, water tanks had baffles in them that reduced "water splashing" or "water movement" inside the tank. Those baffles more or less kept water "still inside the tank"... Back then, it really didn't matter much whether you towed with a partially empty tank or not because there was limited water movement inside the tank.

Those "molded in baffles" took up space inside the tank which reduced capacity or meant a larger tank to carry the same amount of water. As manufacturers started building smaller, ultra-lite trailers led to the need for lighter tanks that carried the same or more water than before, so the baffles started to get smaller or they were eliminated completely. Thats when people towing with half empty tanks started noticing increased sway in some rigs, they also started having "tank problems" like broken straps, tanks falling out of position and split/ruptured tank walls...

Why? A 45 gallon water tank carries about 350 pounds of water (more or less). If the tank is full, that water is essentially "static even when the trailer is moving. But, a half full tank with no baffles, has about 175 pounds of water, swaying back and forth as the trailer moves down the highway. Increase sway, you increase water movement. Sooner or later, you get to a point where you have 175 pounds of weight "slamming against the tank walls" and changing the "balance of the trailer"...

If the tank is in the front of the trailer, there's less movement and the sway is not as noticeable. Same with tanks positioned above the axles. That "slamming back and forth" is not as noticeable and trailer sway isn't greatly affected. On the other hand, if the tank is located in the rear of the trailer, that sloshing is increased. Depending on the rig (tow vehicle, hitch sway control, cargo loading) sway can be "not noticed" or can make a trailer "**** to control on the highway"...

Why? sway induced inside a half full water tank with n o baffles. A few years ago, we had many more reports of broken tank straps, damaged tanks, etc. Keystone didn't start using baffled tanks again, they just changed the mounting system to keep the tanks in position better. We still have "175 pounds of water slamming into the tank ends when we tow with a half full tank"...

Some rigs, depending on how they're set up, will notice that weight in handling difficulty, some better matched tow vehicle/trailer combinations won't notice increased sway at all... But, if you tow "half full" with a tank that doesn't have baffles, you will have an increased possibility of water movement that could damage your tank installation or the tank itself.

How to eliminate that water movement? Tow with a full tank or with an empty tank.

So moral of the story is find out if your tank has baffles or not?

 

[Peto]

I'm pretty sure most modern tanks do not have baffles anymore.

 

[JRTJH]

Dave, Like Phil said, most modern tanks don't have baffles... The "thought" from manufacturers is sort of that in order to maximize interior tank volume, eliminate the molded in baffles and replace that with more water capacity... Their thought (IMO) is to heck with performance reliability, just give the buyer the most capacity. By the time the buyer figures out there's no baffles, the warranty will have expired and if the tank self destructs or he can't fix his sway issues, well, "ain't our problem any longer" ....

Most people with adequate tow vehicles, well matched vehicle/trailer combinations and a good, functional hitch won't see a sway issue, but, a Escort pulling a 16' RPod with a water tank in the rear probably won't ever solve their sway issues if towing with a half full water tank. Not only is it likely a mismatched rig, add in a poor sway control system and then induce sway with a heavy volume of water slushing around "dragging the rear of the trailer with it" and you've got a "recipe for bad towing" and possibly a busted tank strap/failing tank that leaks in 3 or 4 years.....

 

[rlh1957]

We always have water in FW tank. Never know when you’ll want to use your own private & clean toilet.
If you pull in for a nap at Walmart, TS, rest area, roadside or Harvest Host and don’t want to use their bathroom or there aren’t facilities you’ll need some water to flush, wash your hands and face or even quick shower.
Remember carrying the water does add to your payload weight amount.

 

[NH_Bulldog]

Remember carrying the water does add to your payload weight amount.

While it does add weight obviously, whether that weight is factored into the trailer cargo capacity is dependent on what the cargo and loading sticker on each individual trailer states. Just like the ones on tow vehicles, the capacity varies from trailer to trailer.

For example, my Passport’s available cargo capacity was calculated with the fresh water tank full and the waste tanks empty. My Cougar’s sticker says it is calculated with the propane tanks full and all other tanks empty.

To your point though, it all comes down to awareness. Know your numbers!

 

[crowbar-KEY]

Always full.

 

[LERD]

I take them full. I traveled 4 days last fall without a campground stop to get to our destination. It was nice not having to use any other facilities till we were there.

 

[Kzneft]

We always boondock, so no water where we go. Always filled before leaving.

 

[Reddog25]

I'm pretty sure most modern tanks do not have baffles anymore.

My 2025 Cougar 290 RLS has a 75 gallon fresh tank with baffles. I don't know about other makes and models although.

 

[wiredgeorge]

My 2025 Cougar 290 RLS has a 75 gallon fresh tank with baffles. I don't know about other makes and models although.

Just curious... how do you know it has baffles. I never travel with water in the fresh water tank so never thought about it. I think my tank is about 25-30 gallons at most but 75 gallons partly full would feel the water sloshing if no baffles. When I was a member of Mico VFD I often drove a tank truck (OLD OLD deuce & 1/2) and if the tank wasn't full it could actually cause the truck to tip on fast corners and that was really scary.

I do put some water in the fresh tank if camping where it may get below freezing. First time we camped in sub freezing temps, my hose became a frozen rope and we had no water. I had another hose, filled or partly filled the fresh water tank and we has some water for hand washing and flushing. I think that hose may still be frozen hehe. You learn.

 

[Reddog25]

Just curious... how do you know it has baffles. I never travel with water in the fresh water tank so never thought about it. I think my tank is about 25-30 gallons at most but 75 gallons partly full would feel the water sloshing if no baffles. When I was a member of Mico VFD I often drove a tank truck (OLD OLD deuce & 1/2) and if the tank wasn't full it could actually cause the truck to tip on fast corners and that was really scary.

I do put some water in the fresh tank if camping where it may get below freezing. First time we camped in sub freezing temps, my hose became a frozen rope and we had no water. I had another hose, filled or partly filled the fresh water tank and we has some water for hand washing and flushing. I think that hose may still be frozen hehe. You learn.

I know someone at the factory that told me about the baffles.