r/OffGrid • u/aphocks • 6d ago
Emergency Inline Water Storage
Hello my name is Austin Fox, I am a mechanical research and development engineer living in Michigan. I am posting to inquire about an idea that I have. I am looking for basic conceptual guidance from a technical expert about an "in-line water storage device" that I am designing, but with no implication of engineering help or design approval. More a basic overview so that someone who knows about these things better than I do, can say "yeah this has some merit and you should dive into more detail", or "no this is silly, or illegal, or dangerous".
The idea came about from a recent planned water outage we had in my neighborhood. We were informed that we would be without municipal water for a day. Looking online many people discussed filling bathtubs beforehand to have some stored water for filling toilets or other non-drinking needs. I did not like the idea of having to use my tub for water storage, and it reminded me of other times around America where water has been absent for one reason or another, and people suffered because of it. I wanted a solution for having enough safe water for my family for a few days, without having to think about it much, and with it being guaranteed that it was always available.
The concept I have can best be described as an extension of my existing water plumbing that increases the volume of the water in the pipes, and a valve system that allows this increased volume to be isolated and used is the mains are out of service. It must also do this without disrupting or modifying the existing plumbing much, and keep itself clean and low-maintenance for long time spans, while staying safe and immediately useful when needed. I basically wanted my own water tower, without ever having to think about it until I needed it, at which point it would be ready to go easily.
The system taps into the main incoming water line and diverts it through a desired number of modules that are made up of 4-6 inch PVC pipes that are looped down a basement wall or other out-of-the way space. These larger pipes make up the additional storage volume. During normal daily use, these storage pipes are continuously flushed and refreshed with clean drinking water. During an emergency, the mains and home plumbing can be isolated from these larger pipes and the clean water inside of them acts as a reservoir for a few days until the issue is fixed. The outlet is gravity fed from the larger pipes, or a small hand pump can be attached. Each module holds about 20 gallons, and multiple can be assembled in series. This modular design makes isolation, maintenance, and scaling easier.
Aside from the overall concept I also wanted guidance about how necessary a Reduced Pressure Zone Backflow Preventer is? I understand that most municipalities err on the side of requiring them for unknown devices, but since this device is primarily just a pipe extension, I am hoping it is not required, as it is costly and requires inspection.
please let me know what you guys think, and see attached drawings for a very loose initial idea sketch.
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u/LordSilveron 6d ago
Complicated and undersized. That looks to be 4" pipe with 18 ft sections. The horizontal will hold roughly 10 gallons each. Standard survival consumption is 1 gallon per person per day. That's drinking, cooking, and minimal hygiene. You'll also need insulation from our winters and need to find space to put this, frankly, bulky and unsightly beast. Our cohort from PR is spot on with a small tank. You've got 6 home depot buckets of storage. Honestly, you'd be better off with an old water heater tank. All the hookups are there, fill, drain, and insulated as a bonus in a much smaller package.
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u/ZeniChan 6d ago
My parents live in Mexico in a more rural area with a water co-op that only delivers water zero to two days a week on an unpredictable schedule depending on the season. So all the homes (expats and locals) have a cistern as standard. The size depends on how long you want a water buffer to last and your domestic usage. Commercial cisterns range in sizes from 1000 litres to 50,000 litres depending on the home. Though more commonly, the locals use one or more 1000 litre IBC tote tanks have become popular recently for above ground storage and they put them on the roof for gravity feed of the water with no need for a pump. Super cheap too. Underground cisterns use a simple float valve to refill if the water comes on. A popular location to put the cisterns is under a detached garage pad located higher than the house to allow gravity draining if there is no power.
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u/Rubik842 6d ago
Smokey Yunick did this with fuel lines in a racecar. regulations limited the tank size.
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u/Crab-Tree-319 5d ago
I put in two passive tanks that can handle the water pressure of the house. Water is constantly flowing through and supplies the whole house so no stagnation. Setup allows for isolation and bypass but is set to flow through both tanks. Capacity is around 220 gallons of emergency water. Can throw on a rv pump or similar in a true emergency or just access through the boiler drains with buckets or hoses. Minimal footprint and cost about $800 in material at the time of install. No more rotating water and still enough supply for the whole family in an emergency for 14 days. Needed vacuum breakers as these tanks can’t handle negative pressure and check valve before so no backflow if city main runs out or is shutoff.
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u/Lucky_Good_4386 6d ago
I'm not sure how viable the idea is in existing homes. It would be nigh on impossible to get a system like this in my house. Not to mention apartments, but this is offgrid after all.
For newer builds it might have merits if integrated properly. But if I did build a new home and wanted water storage of sorts in case of a disruption, I could put in a cistern of sorts, but I'm sceptical as to how water quality would be affected.
How does your pipe system differ from a cistern that fills and drains continuously?
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u/JayTeeDeeUnderscore 6d ago
Well ballast tank/bladder tank will hold more and keep it at useful pressure.
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u/Least_Perception_223 6d ago
This seems overly complicated
I have a house in puerto rico and we face water outages on a regular basis.
We have a cistern with a float valve in the top. Our city water supply feeds the float valve.
The house is connected to the cistern with a pump.
This way we always have 250 gallons of water available that acts as a buffer during outages.
Water in the cistern is constantly refreshed when everything is normal
When the city water goes out - we do not even notice