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Old 10-24-2020, 12:42 PM   #1
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Fresh Water Holding Tank Mod

Whilst taking a shower this morning, park lost water pressure. Hasn't done that before that I am aware of. Got out, put towel on, marched to monitor panel to laughter of seeing Dad covered in soap, turned on water pump, heard it start, went back to shower, and water quits about time that I am getting back in. Empty Tank. Grrr.

In a previous trailer, I setup a fresh tank auto-fill by using a dizzying assortment of flow meters, electric valves, peristalic chemical pump, additional tank sensors, and so forth. Worked great, but I was only one that could work on it. Upside is, I didn't breach the tank. Downside was extreme complexity and cost. Goal Acheived: Complete autonomy for fill / sanitize / chlorinate / RO feed / RO Bypass / Low Water Warning (via Pump) / Dual filter auto changeover / and on and on. Of course everything goes sideways when battery hit less than 12vdc and microcontroller crashes. Coach essentially ran off tank 100% of time, and slowly refilled off RO (when in park).

As tank doesn't maintain pressure (at least it shouldn't), I am wanting to cut a 8" hole in top and add a water proof marine access hatch. That will allow me internal access to tank interior to add float valve for tank to fill automatically. Water comes in via typical, goes to tank float valve, and tank fills up. Water pump pressurizes trailer.

After the hot mess of first auto-fill project, wanted some 3rd party critiques before I get started on this one.

So, What Say You All?

FWIW, this will be frankenstein-ed into a 35G holding tank in mechanicals area of forward storage compartment of 2015 RBD Royal Travel 37AL. Protected from elements, don't have a oh-crap drain pan yet...
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Old 10-24-2020, 01:58 PM   #2
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Seems like a lot of work for small gains.
If you are bored and like to over engineer stuff then go for it.
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Old 10-24-2020, 02:48 PM   #3
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Cut the access hole, add the cover, and put a float valve thru the side of the tank.

The parks water supply goes to that.Click image for larger version

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Old 10-24-2020, 09:51 PM   #4
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Not a lot of work, I dont think. One end of fresh tank is wau too easily accessible - not being sarcastic. Previous trailer was used everywhere, and on several occasions where we were at was questionable. IE small RV Park that had great tasting water but was so hard hose screens clogged within a week.

Softener took care of that with push of a button. System took over the rinse / flush / rinse of media bed. Also monitored water for Total Dissolved Solids and would switch to RO for cleanup. BTW, RO is not near as wasteful as residential setups when you are pressurizing input and filling a non-pressurized tank. Lowest it ever got was half-quartish, highest is half gallon per gallon stored. Often times, due to softener and pre-filtration I could send waste water back through. Membrane life did not seem to be affected. I preferred to have a great amount of control over my water (drinking, bathing, cooking). Waste water was stored and pumped to toilet and tank rinsers.

I want to get back to the same point as close as I can. But much simpler this time. Eliminating flow meters for tank fill / use / drain (yes, 3 flow meters) cits down a huge amount of complexity. If I am able to modify the tank as I envision, then rest of systems will be left in place with bypass for emergency and mainyenance needs. First system purified water that rivaled Distilled. I want to get as close to that as I can.
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Old 10-24-2020, 09:59 PM   #5
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Originally Posted by twinboat View Post
Cut the access hole, add the cover, and put a float valve thru the side of the tank.

The parks water supply goes to that.Attachment 305777
Yup, pretty much the idea that I had in mind bit valve I would use is much more compact on the float.

My tank is on the order of 40 inches long, about 12 inches is exposed without pulling it completely, and can slide it another 10 inches before I have to move something or other.. Do you foresee any problems making cutout so close to edge?

My thoughts are it would be beneficial as there is much less flex of top tank panel, and would be less stress / wear on marine hatch & cover and drilled holes. Just would need to stay away from tank corners where vent and fill are located.
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Old 10-25-2020, 10:48 AM   #6
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A lot of Class A coaches have auto fill systems for their fresh water tank. They operate on fill sensors and glow meter, most are programmed to the tank. I would look into how they are setup.

The other option is you will need a food safe material (like used for cutting boards) to make a lid to cover your access hole for your tank. You could use stainless nutserts the secure the lid. You can buy bungs online at some RV supply houses to set you fill line at the top of the tank to make it easier to use your float valve. While you are at it you should install a bung in the bottom of the tank so you can allow it to fully drain. Side drains always trap a few gallons of water in the tank that is never completely removed.

Just a few thoughts, hopefully your project works out well.
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Old 10-25-2020, 05:49 PM   #7
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Where is water tank located on coachmen freelander 2019 model
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Old 10-25-2020, 10:47 PM   #8
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Why tap the tank? Use a parallel pipe with a float switch in it, and a solenoid valve for fill.
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Old 10-26-2020, 12:17 AM   #9
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FWIW, my water tank has a 3" threaded plug in the top, from the factory. The problem will be how to thread your tank. Of course you may use a 3" rubber cleanout plug after you figure out how to cut the hole.
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Old 10-26-2020, 07:35 AM   #10
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I cannot believe I didn't think about using a "mechanical" plug. I saw the inflatable test plugs, and dismissed them due to eventual failure of bladder getting torn.

My first design used flow meters and solenoids, but became very complicated. Battery got low, then microcontroller crashed and I lost all functionality. Goal here is to "KISS" it.

Its funny that nylon cutting board material was suggested. I toyed with that for a couple weeks, even went as far as doing a few mockups on the old tank I ruined from the previous trailer. Just could not find a way to clamp down the "seal flange" enough to keep water from leaking past 1) Oring or 2) foam tape or 3) seal band of rtv laid in a routed channel or 4) rubber block glued to seal flange. All methods leaked because couldn't clamp tight enough. Nut inserts pulled through very easily, even when backed up by a washer. Best success was using flange head screws inserted from tank interior with rubber washer, and secured using nuts and washers on top. Tried to use stainless t-nuts, nylon couldn't hold well enough.
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Old 10-26-2020, 07:58 AM   #11
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Originally Posted by rgvtexan View Post
Why tap the tank? Use a parallel pipe with a float switch in it, and a solenoid valve for fill.

My water pump is a Delavan 5850 rated at 5gpm and 60psi. I do use an accumulator tank. Trying to keep this basic function electric free, as it adds a lot of complication in a hurry.

Using a "parallel" pipe would mean it has to be connected via 1/2" fill and suction ports on water tank. My previous system used this initially, but despite off pipe being 6 inches dia, the pump was able to suck it down and draw air. The tank ports wouldn't flow enough water, unassisted, to maintain water level inside secondary "tank".

I would prefer to keep my water tank intact, but have not been able to work out how since I have only 1 draw port (for pump).
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