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MCI 102-C3 coach to RV - Water System

Quick and crude water tank sketch for ya. I don't doubt that I'm explaining it well enough to be understood correctly, but pictures help. There will be extra filtering apparatus in between the pump and tank.

Pump pressurizes up to 100 psi (set to stop at 80-85 psi here). 9-gallon expansion tank sitting higher than the 52.6-gallon water tank. Total air volume of 61.1 gallons at 0 psig. Pump begins to flow water into the water tank and the pressure air pressure begins to build. By the calculations above, if they're correct, the water tank will fill close to the 52.6 gallon max and the expansion tank should measure around 80 psig.

The four blue hose off the bottom of the water tank would lead to fixtures and would theoretically already be filled with water regulated to around 40 psig. No pump needed to supply the fixtures because the lines would already be pressurized by the expansion tank. I would be inclined to also add a regulator on the expansion tank so that any pressure reading above 85 psig would bleed off to the atmosphere or a cutoff switch to stop the pump as protection.

The reason behind this whole setup is to still use only one water pump who's pulses are completely buffered by pressure tanks and all fixtures see the same flow and pressure no matter what valve gets opened up. Surely, you guys know how annoying it is when you hop into a nice, hot shower on a cold morning and your wife decides to start a load of laundry on hot water immediately after you've began your shower. I'm still setting this up to be able to scab in another pump for the fixtures in case pressurizing the rectangle water tank is in no way feasible. The high-pressure pump is a necessity for the RO filter system to operate, so I might as well utilize that back pressure that will already be available.

582.jpg
 
aczlan said,
JNHEscher said:
Noted. So we're on the same page, I'm shooting for the water tank and expansion tank to start at 0 psi and end up at 80 psi once the water tank is filled. A better explanation would be that the water tank and expansion tank are connected via small air line, both begin with 0 psi and as the water tank fills up, the air inside it is displaced to the expansion tank to create pressure (hopefully around 80 psi). That's probably obvious, but it makes better sense. Works just like a bladder tank or well pressure tank, only with the holding and expansion tank being two separate vessels.

Edit: Kinda curious what your numbers were in the formula. Currently using a stainless tank with an internal volume of 52.6 gallons and an expansion tank with an internal volume of 9 gallons and an RO system maximum pressure of 85 psig, I'm at this -

psia1 x v1 = psia2 x v2
psia1 = 14.7 + 0 = 14.7
v1 = 52.6 + 9
v2 = 9
14.7 x 61.6 = 9 x psia2
905.82 = 9 x psia2
psia2 = 100.6

That gets me durn close the 99.7 psia I would need to see in the tanks when at max water holding volume of 52.6 gallons. At least that's what makes sense on paper right now.​
Not sure how I got to there now as I get different numbers now.
IIRC, I was using P1= 94.7PSIA, P2=15.7PSIA and V2=49 gallons..

Are you planning on running multiple pressure regulators, or a single one and then a distribution block off of the tank?
I would be inclined to plumb it: 0PSIG holding tank > 80PSIG pump w/pressure switch > 9 gallon bladder expansion tank > 40PSIG pressure reducer > distribution block.
That should get you enough pressure stored in the tank to stop the "yo-yo water pressure" effect and let you run your RO filter from the 9 gallon tank before the pressure reducer.

Aaron Z
 
Pt_Ranger_V8 said,

The only downfall I see with using an air tank to pressure your water tank is how are you filling the water tank?

Since the pressure will equalize, won't you need pressurized water to fill the tank?

Edit: I'm assuming you're setting this up like a household well + pressure tank. If you're not, ignore this post.
 
[486] said,

that's one huge balloon you're making out of 1/4" plate

Interested to see what sort of baffle/bracing arrangement you come up with
 
aczlan said,
Pt_Ranger_V8 said:
The only downfall I see with using an air tank to pressure your water tank is how are you filling the water tank?

Since the pressure will equalize, won't you need pressurized water to fill the tank?

Edit: I'm assuming you're setting this up like a household well + pressure tank. If you're not, ignore this post.​
As I read the diagram, he is planning on having a 2nd tank that is filled with air to act like a bladder and filling the 50ish gallon tank with a 80PSIG pump.
As the 80PSIG pump fills the 50ish gallon tank, it pushes the air out and up into the air tank, the air then comes out as you use the water in the big tank (until the pump cycles back on).

Aaron Z
 
aczlan said:
Not sure how I got to there now as I get different numbers now.
IIRC, I was using P1= 94.7PSIA, P2=15.7PSIA and V2=49 gallons..

Are you planning on running multiple pressure regulators, or a single one and then a distribution block off of the tank?
I would be inclined to plumb it: 0PSIG holding tank > 80PSIG pump w/pressure switch > 9 gallon bladder expansion tank > 40PSIG pressure reducer > distribution block.
That should get you enough pressure stored in the tank to stop the "yo-yo water pressure" effect and let you run your RO filter from the 9 gallon tank before the pressure reducer.

Aaron Z​
Probably multiple water pressure regulators. Water line runs will range between 5' and about 40' through 3/8" PE-RT so higher pressure for the longer run would be nice.

I'll think on the arrangement some more. Currently it goes: gutters>filter>rain water tanks>80psi pump>pressure tank>UV filter>RO filter>holding tank with expansion>home runs. RO filters are miserably slow so I plan to put two or more in parallel. They require quite a bit of pressure to work properly and they're set up to work with the backpressure from the filtered water. Because of their sluggishness, I need the holding tank so we have a decent amount of filtered water ready to go at all times and the backpressure they create works great for pressurizing the rest of the system thereafter.

Going as big as I can with the pressurized holding tank because of how slow the RO filtration is. This would give us a sizable reserve at all times that would begin refilling as soon as the holding tank pressure began to drop below X pressure because there would be a near constant 70-80psi pushing water through the RO filters. With pressure and volume of gas being inversely proportional, a 52ish gallon capacity should put out a constant 26ish gallons of water before dropping to the 40ish psi that the home runs will be regulated to.

Hope all that makes sense. It is rather complicated compared to most other RV systems. This setup should eliminate all the typical nuisances of mobile systems though.
[486] said:
that's one huge balloon you're making out of 1/4" plate

Interested to see what sort of baffle/bracing arrangement you come up with​
Tons of bracing and a bit of baffling. I know square pressure vessels aren't suitable. The long sides would sit against the subframe tubes that are 3/16" steel with gussets welded inside about every 12". The underside will be supported by numerous, heavy-wall square tubes. The top will be braced about the same as the bottom. End caps will have more square tube bracing. Quite a bit to convey of an area that's hard to view and even with all the bracing it's still asking a lot for a box to hold that pressure.

My dimensional limitations within this pit area are 7.875" high, 32.5" wide, and 52" deep. I can make room to fit cylindrical tanks with an 8" diameter. My goal to maximize water holding capacity was the reason for the box tank. Looked all over and couldn't come up with stainless hot dog tanks to fit in the pit and fill it out for max water capacity. If there's tanks out there that fit, I'm all for switching so that I'm not dealing with bracing the hell out of a square tank.
 
FirstRam said,

I have no doubt you will make this work as planned. Anything worth having is worth working for, and you've been working your ass off!
 
CarterKaft said,
[486 said:
;44475764]that's one huge balloon you're making out of 1/4" plate

Interested to see what sort of baffle/bracing arrangement you come up with​
No shit, this part scares the shit out of me...
Have you ever built a square tank of any size? They flex like a mofo at very low pressure, a 80 psi tank that big is not something I would want anywhere my personal space. A failure in that tank with low water volume would disintegrate a human, not trying to be like the safety dick but that is scary as fuck.
Are you going to proof test? At least double operating pressure? A grease gun hooked to a water hose will get you a easy hydro tester.
 
I will absolutely be testing it. Already ran the numbers and it makes me very leery of the idea. Still sifting through cylindrical tanks to stuff in place and finding very little that I like. There's gotta be an option out there because it's not like there hasn't been a few thousand variants of pressure tanks manufactured. Like most everything on this project, there's going to be an answer found if I look long enough.
 
[486] said,

you can get tank heads relatively cheap, probably even in stainless, then ask around to your steelyard about slip rolling some 1/8" stainless sheet for you into the tank bodies
 
[486 said:
;44476630]you can get tank heads relatively cheap, probably even in stainless, then ask around to your steelyard about slip rolling some 1/8" stainless sheet for you into the tank bodies​
Link? I started browsing tank heads a while back and kept running in to sites that required an account and such. Figured ordering heads and getting stainless tube cut for me to weld would be the way to go until the cost added up. We're set on putting $1k+ into it now that I've tallied up every option and come to around $1k no matter what.

I had these two tank links saved from the last time I was looking for pre-made cylinders in sizes that I could fit. Stainless is preferred over alu. I can fit seven of them, totaling around 35 gallons.
https://www.summitracing.com/parts/a...5100/overview/
https://www.x2industries.com/product...tank-32-x-8-5/ <this one will undoubtedly be made in China.
 
[486] said,
JNHEscher said:
Link? I started browsing tank heads a while back and kept running in to sites that required an account and such. Figured ordering heads and getting stainless tube cut for me to weld would be the way to go until the cost added up. We're set on putting $1k+ into it now that I've tallied up every option and come to around $1k no matter what.​
google says to call these guys
Contact | Our Locations | Commercial Metal Forming

don't buy tubing, buy sheet and have it rolled
doesn't need to be perfectly round, just round enough
 
[486] said:
google says to call these guys
Contact | Our Locations | Commercial Metal Forming

don't buy tubing, buy sheet and have it rolled
doesn't need to be perfectly round, just round enough​
On it. I have them and Baker up for calls tomorrow. Fingers crossed that either will make a small order for me. Pics of what I can fit if I make the tanks. Six 8.5" diameter transverse mount or four 8.125" diameter longitudinal mount. Both total right around 43 gallons. With round tanks, I can cut out the spare tire bay firewall to extend the tanks forward another foot or three if I really wanted to. I already measured the tire bay and there's not enough height to stack two 315's so there will be ample space.

583.jpg
584.jpg
 
CarterKaft said,

I found a paper on a nuclear storage facility rectangle close to your size.

The pressures are lower at 37 operating and 55 PSI design but the math should be right.

https://www.osti.gov/servlets/purl/6667698/

edit: Have you seen the Everlanders Earth Romer keg tank water system? its pretty simple and tanks would be easy to source most anywhere in the US.

https://youtu.be/1THtBYxu8N8
 
aczlan said,
CarterKaft said:
I found a paper on a nuclear storage facility rectangle close to your size.
The pressures are lower at 37 operating and 55 PSI design but the math should be right.
https://www.osti.gov/servlets/purl/6667698/​
3/4" plate sides and baffle? That should hold it...
CarterKaft said:
edit: Have you seen the Everlanders Earth Romer keg tank water system? its pretty simple and tanks would be easy to source most anywhere in the US.
https://youtu.be/1THtBYxu8N8​
Very interesting, I was looking for those on fleabay, but couldn't remember what they were called.

Aaron Z
 
CarterKaft said,
aczlan said:
3/4" plate sides and baffle? That should hold it...
Aaron Z​
1" baffle LOL.

I know a Nuke plant project is going to be super conservative but the maths don't lie. Since OP is good with maths he might get something out of it.
aczlan said:
Very interesting, I was looking for those on fleabay, but couldn't remember what they were called.
Aaron Z​
It's a pretty cool system and they use one with a sous vide heater to make hot water for their outdoor showers.

For the OP I am not sure what the aversion is to rotomolded tank with conventional pump. I have a RV with a conventional pump system and the fancier 4 way ball valve inlet that allows you do easily accomplish most any task. The pumps are so cheap and importantly easy to repair I can't imagine a need for a different system in conventional RV with space for conventional cube tank.
 
CarterKaft said:
I found a paper on a nuclear storage facility rectangle close to your size.

The pressures are lower at 37 operating and 55 PSI design but the math should be right.

https://www.osti.gov/servlets/purl/6667698/

edit: Have you seen the Everlanders Earth Romer keg tank water system? its pretty simple and tanks would be easy to source most anywhere in the US.

https://youtu.be/1THtBYxu8N8​
CarterKaft said:
1" baffle LOL.

I know a Nuke plant project is going to be super conservative but the maths don't lie. Since OP is good with maths he might get something out of it.



It's a pretty cool system and they use one with a sous vide heater to make hot water for their outdoor showers.

For the OP I am not sure what the aversion is to rotomolded tank with conventional pump. I have a RV with a conventional pump system and the fancier 4 way ball valve inlet that allows you do easily accomplish most any task. The pumps are so cheap and importantly easy to repair I can't imagine a need for a different system in conventional RV with space for conventional cube tank.​
This is why I love the PBB and stuck the build here. The nuke tank is rather fascinating. Pretty encouraging, too, but I know we won't be using that much stainless. Gets costly. I did get quotes from EMJ out of Denver today. 5x10 of 1/4" is $1,116. Only a few bucks more than a 4x10 so we would buy the extra and have plenty left over to replace several other panels. No tank head manufacturer that I called today would make heads as small as I would need, but I was referred to Jason with CMF. Called and left a message. Might have to call again tomorrow.

Not once did Pepsi tanks ever cross my mind. The 5-gallon tanks are 8.5" diameter. Score #1. Height of 24.75", might be close enough. 130 psi max, bingo. Looks like the cost would be around 1/10th of making anything myself. This might be the route to go because I want tanks that I can easily clean out and the interconnects are a piece of cake.

I'm not entirely sure what my aversion to poly tanks is. We've looked them up several times. Nothing fit quite right and the cost of every arrangement we put together didn't really make them worthwhile for what we want to do. I may still come up with poly tanks to use for the rain water holding. The reason the pressure vessel came up is because we are using an RO system which requires pressurized water. Because that pressure will already be available after running through the RO membranes, I thought I might as well continue to use that pressure to complete the system rather than tacking on more pumps that use more power. That and a pressure tank is kind of a must to stop the pulsation that diaphragm pumps generate. I plan to use the Shurflo 100 psi pump.

On this pressurized holding tank that I've been mumbling about, the separate expansion tank was planned so that I could completely fill the holding tank for maxing water capacity. I could easily stick with the single tank and run the numbers to see how much water I could pack in when max psi hits. I really like the Pepsi tanks, though. Glad you brought those up. Cheap and highly functional for the purpose is a win win.
 
Java said:
The Pepsi kegs are also known as cornies FWIW. They are great.

Sent from my SM-G973U using Tapatalk​
Found that. Gotta try all the keywords on the local Craigslist. Hopefully I'm not competing against the thousands of brewers here. Everybody and their grandma in Colorado wants to brew.
 
Java said,
JNHEscher said:
Found that. Gotta try all the keywords on the local Craigslist. Hopefully I'm not competing with the thousands of brewers here. Everybody and their grandma in Colorado wants to brew.​
Ha! Yep, your competing with all the homebrewers. Get ball locks if you can.
 
Found several cornies in Denver, so I think the boys and I will ride along with my wife at the crack of dawn when she heads to work Wednesday. We'll have to kill 12 hours until she clocks out, but for the price of these things, it's well worth it. Looks to me like they're the way to go because they accomplish everything I had in mind. Honestly, I can't believe we were so close to pulling the trigger on something else ten times the cost before Cornelius tanks came up. Pays off to load a thread with gibberish, I guess lol.

Did a quick mock-up with the general dimensions. I should have no problem fitting eight tanks into the designated space. They do interfere with each other by 0.75". Since the hand holds look to be plastic, I'm pretty sure I can notch them down enough for everything to fit just right. Quick search for tanks brackets should get me some hoops to hold them in place.

586.jpg
 
Java said,

I have two here if you want real world numbers. You need some clearance for the fittings on the top.

But parts and orings etc are easily available!
 
Java said:
I have two here if you want real world numbers. You need some clearance for the fittings on the top.

But parts and orings etc are easily available!

Sent from my SM-G973U using Tapatalk​
That would be stupendous. Only if you're willing. Just a picture of two of them butted up against each other in perpendicular manner like I have pictured would help a lot. The fittings look like they're splayed enough to clear, but I'm not sure how tall the ball locks are. I know I can't really change the nipples any because of how they seat the dip tubes.
 
CarterKaft said,
JNHEscher said:
Found several cornies in Denver, so I think the boys and I will ride along with my wife at the crack of dawn when she heads to work Wednesday. We'll have to kill 12 hours until she clocks out, but for the price of these things, it's well worth it. Looks to me like they're the way to go because they accomplish everything I had in mind. Honestly, I can't believe we were so close to pulling the trigger on something else ten times the cost before Cornelius tanks came up. Pays off to load a thread with gibberish, I guess lol.

Did a quick mock-up with the general dimensions. I should have no problem fitting eight tanks into the designated space. They do interfere with each other by 0.75". Since the hand holds look to be plastic, I'm pretty sure I can notch them down enough for everything to fit just right. Quick search for tanks brackets should get me some hoops to hold them in place.​
I'm glad you found the info useful. I always struggle with weather or not to suggest another way of doing something because I know I am as hard headed as the next guy.
 
Java said,
JNHEscher said:
That would be stupendous. Only if you're willing. Just a picture of two of them butted up against each other in perpendicular manner like I have pictured would help a lot. The fittings look like they're splayed enough to clear, but I'm not sure how tall the ball locks are. I know I can't really change the nipples any because of how they seat the dip tubes.​
Perpendicular the fittings look to nest nicely.

Overall with the fittings is about 25.25"
1e834ee604d6dd15476886ad398492c7.jpg
 
CarterKaft said:
I'm glad you found the info useful. I always struggle with weather or not to suggest another way of doing something because I know I am as hard headed as the next guy.​
Bring it on, man. Your research/experience has been better than mine, from what I remember you posting. Sometimes I scratch my head and my ass over this stuff for far too long.
Java said:
Perpendicular the fittings look to nest nicely.

Overall with the fittings is about 25.25"

Sent from my SM-G973U using Tapatalk​
That's an extra half inch to deal with. Although, your first pic looks as though you might have had the lens looking straight down. I have exactly 32.5" to fit these into and the perpendicular assembly appears to land damn near on 32.5". This is going to happen. I mean, six tanks will suffice, but if I can cram in eight....

Adding this because I'm not sure if the plastic fittings can take up to 85 psi under a lot of vibration. https://www.morebeer.com/products/to...ess-flare.html
And this may come in handy:
Dip Tube O-Rings
5/16″ ID x 1/2″OD x 3/32″ width
9452K172 BunaN #109
Pkg 100/$1.89

Post O-Rings
7/16″ ID x 5/8″ OD x 3/32″ width
9452K23 BunaN #111
Pkg 100/$2.15

Lid O-Rings
3 1/2″ ID x 4″ OD x 1/4″ width
9452K218 BunaN #417
Pkg 10/$12.50
 
Java said,

Fittings are pretty stout. And yes Orings are easy to get. The lid uses a large oring as well.

Yes it was right at 32.5" when perpendicular. If its REALLY tight you may be able to shove them a little tighter. The tops and bottoms are a hard rubber, may have a little give.
 
Looks like all the corny tank measurements are working out more than perfectly. This is excitingly surprising, yet not surprising at all. It's a lot like how the electrical junction boxes fit right in the center chase and then the PVC conduits laid right in like the bus was made to accept these parts and materials.

That said, I'm making a note for myself here. For eight corny tanks, I need 7 gallons of expansion tank. With the 1.5" square tubes being welded on top of the subframe beams, I have 6" of height left over between the tops of the square tubes and the underside of the floor. I found 5-gallon 6" diameter air tanks on Summit. One for each side and their 7.5" height on their feet fits right in. As a bonus with the 1.5" square tubes running transverse to the bus, I can place them to be the telescopic slides for the slide-out wheel tubs I was planning because they will protrude towards the wheel arches right where I would need them. I may need to grab another stick or two for this, but this arrangement will allow for the slide tubes to span the full width of the bus and remain seamless so that slider alignment is highly accurate.
 
10 for $300. Went ahead on got the two spares. Not as cheap as some. Not as expensive as others. Still a good deal from some genuine fellows at Whiskey Barrel Coffee in Denver. Pretty cool small fab shop they have in back where the kegs were and awesome antique coffee machines up front.

Good thing the guy I was talking to announced the two different tank styles. The first ones I looked at had both nipples on the same side. Caught me off guard. He explained that the kegs up top were the tall, skinny ones and the bottom was the short, fat ones. The short ones were 9x22's that were originally pin locks that had been converted to ball lock. Tall ones are the actual Pepsi kegs that are in fact 8.5x24 with nipples on opposite sides. 9" diameter tanks wouldn't have fit. I'm still chuckling at how much lighter they are than that 400-pound stainless box was going to be (not including the water).

594.jpg
 
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