Let’s say Jeff Bezos was hell-bent determined to build a new home with an interesting feature: plumbing that absolutely would not have to be serviced anytime within the next few hundred years. The pipes WOULD NOT crack. The fixtures WOULD NOT fail. The drains WOULD NEVER clog. And so on.
And Bezos was totally determined to throw whatever cash was necessary to throw at the engineering and materials to make it happen. If it ended up costing a few billion to plumb a 2500 sq ft ranch home, then by gum, he’s willing to bankroll it.
So. As strictly an engineering problem, can a home’s plumbing be made THAT reliable? A few hundred years of reliability? Can the pipes be made huge so that you can pour down all the grease, hair, and food you want? Can the pipe material be something that never (essentially) corrodes and is impervious to water over time? Can the hot water heater be made as something that will (essentially) never crack or corrode? Would a lot of the plumbing have to somehow be made flexible to account for ground settling and such?
If you put something down the drain that will stick to the inside of the pipes, then no matter how big the pipes are, eventually they’ll clog. Larger pipes might delay that, but it’ll happen eventually. So now you need pipes that either nothing will stick to (which probably isn’t possible), or which somehow clean themselves.
PEX supply plumbing will last effectively forever. So will PVC drain plumbing. So unlike in Dayes of Yore, the couplings and piping itself are not life limited if skillfully installed with proper allowance for thermal expansion, building settling, bend radius, earthquake survivability, etc.
Fixtures are a weak point because there must be mechanical movement to control the flow. Water heaters must deal with thermal expansion. Supply plumbing carries water but also carries dissolved solids and granules of gunk. That stuff builds up someplace unless it can flow all the way through uninterrupted. Ditto, ref @Chronos, stuff that goes down drains tends to stick to pipes at least a smidgen. Anywhere water evaporates will accumulate calcium scale. Whether that’s inside a faucet nozzle, inside a drain, or on the exterior surface of a fixture.
Speaking of which, supplying only fully distilled water to the house is probably one of the cheapest most practical plumbing life extension projects that are actually real-world doable. Net of replacing the whole distilling rig every few years and meanwhile servicing it periodically.
Our civilization has figured out how to build nuclear reactors, so I’m sure that given enough money, we could at least engineer a bulletproof water supply and sewage system. Make it big enough, use robust materials like high-nickel steel, use diameters that are unlikely to ever clog under heavy residential use.
The part that I wouldn’t bet on is any kind of everlasting boiler. I’m sure you could make one that lasts decades, but centuries? That seems tough to me. It would have to be engineered to self-clean any mineral residues, it would need stuff like thermocouples that aren’t famously durable, etc. Perhaps it would be something totally off-the-wall like microwave-heated, gravity-fed, forged with very durable alloys or plastics. Supply it only with deionized water (and now we need to design a forever-deionizer).
I’m just spitballing, don’t hold me to any of that. Pretend I’m Elon Musk.
If money was no issue, it would be possible to have pipes which were almost frictionless on the inside. Highly polish them and make them out of a hydrophobic material which would repel most material from sticking. Some upgraded toilets are made this way. The bowl is highly polished so that it doesn’t stain as easily.
Does shit stick to Teflon? Does cooling or cold grease?
Maybe we install a 1920s style disintegrator ray as a kind of super garbage disposal in each drain stem below each basin or tub or whatever. Convert anything / everything passing through, including water, into just loose protons, neutrons, and electrons that vent to the room air. So no drain plumbing at all.
The disintegrator can be all modern electronics with a theoretically unlimited life if we run it close enough to thermal equilibrium.
Ref @HMS_Irruncible’s fine suggestion I’ll call Musk and get him on this one right away. It should be ready about 2024 give or take a couple decades.
You could design a system to be self maintaining but that might just add additional failure points to the system. I would probably go with a 316L stainless steel piping for all of the drains with a high polish on the inside and I’d run 6" pipes for the whole waste side. This is basically a sewer system at that point so you should see very little clogging. I’d also add a little extra slope to all of the main runs probably to 1/2"/foot. That would basically eliminate any issues on the home side.
I would eliminate mixing valves and make everything independant ball valves and I’d make all of the ball valves stainless too. There is basically no way for them to fail at that point. The hot water generation would be the hardest point. I’d probably use a boiler to heat the house and then run a large steam leg off of that thought a steam/water stainless heat exchanger. I’d designed the exchangers for ~1mm btu/hr so even if there was a loss in efficiency over time it would still be effective. All water into the house would run through bed filters. Assuming 100 gallons per day we’d need a bed filter about 18.25 cuft to treat the water and give us 20 gpm. I’d probably put an equal size sandbed filter in front of that. After the carbon I’d run through a water softener and again I’d size the salt (potassium chloride) reservoir so it didn’t need to be refilled for 100 years so about 52,000 pounds of salt or about 30 cuft.
The boiler system should be a closed loop system filled with RO/DI water and treatment chemicals. Right now closed loop boilers can get to 50 year expected life spans especially when we build them from stainless vs cast iron. Some basic burner maintenance and stuff would still be required but you could probably oversize it and just take the efficiency hit rather that do the service. That plus a little luck may get you to 100 years. I’d also try and design the system so that it constantly used the boiler rather than putting thermal cycles on the boiler. Since we have infinite money I’d dump heat in the summer into a geo reservoir and then try to utilize the ground loop for additional heating in the summer the goal would be to have the boiler operate at 80% basically constantly.
I worked 13 years in water damage mitigation and my conclusion is that if you want to have plumbing, you’ll need to accept the possibility, however slight, of having a water loss.
I’ve seen every type of plumbing pipe fail: copper, galvanized, PVC, CPVC, PEX, polybutylene. Nothing seems to be immune.
I’ve seen every plumbing fixture fail in a multitude of fashions: water heaters, toilets, showers, sinks, dishwashers, washing machines, aquariums, sump pumps, icemakers, and air conditioners.
Supposing you did engineer a perfect home plumbing system, all it takes is for your 5-year-old to clog the bathroom sink and leave the water running and you’re back at square one.
Probably not impossible to accomplish, but there are far less expensive ways to minimize risk if that’s what you’re after.
That could actually work. Dig a hole deep enough and the waste would be boiled and/or burned off by geothermal heating. Tricky part would be to design the venting gas to not come up the pipe the waste goes down.
All engineering problems are tradeoffs between capital cost, maintenance cost, safety, operability, life, etc. A few hundred years of reliability through hurricanes, earthquakes etc. can be done but will make capex or opex or other things very expensive.
Typically chemical plants, where there is lot of piping, have a design life of 20-30 years. Many nuclear plants fall into this category too.
This stuff will transport boiling sulfuric acid and I’ve used it for transporting molten metals at up to 1500 degrees F. Should handle your crapper for quite some time. Especially since you can use boiling sulfuric acid to unclog it.
A pit deep enough to hold a couple centuries’ worth of a large household’s output, or to take it down to geothermal destruction depths should be deep enough to have the inputs reach terminal velocity on their way to oblivion. Heck, if you do it right, the pee will turn into virga on the way down, so you don’t need to allow for storing that volume at all.
I’m with oredigger77. I have runs lots of stainless tubing and that is an easy choice for the water supply. All valves are quarter turn stainless steel ball valves with Teflon seals. This is standard military/space-rated piping. Waste lines can also be stainless steel and since they are not pressure rated I would use easily available vacuum piping, schedule 5 or 10 (thin wall). They have long radius turns for better flow. Teflon sealed quick disconnect clamps at all joints. Install view ports if you want easy inspection. All this is actually easy to install. Chemical polished insides if you want. The fixtures and appliances are always going to be the weak point.
When we visited Thailand I was surprised to see stainless steel gutters and downspouts leading to stainless tanks to hold the rainwater on higher end houses. Some of the tanks were formed to copy the traditional pottery tanks used for this purpose. Why isn’t this system available elsewhere?
A few hundred years is a very long time for anything. I would worry that any polymer would survive. Plasticisers have a habit of leaching out over time so flexible plastics become brittle. The chance of an evolved greebly working out how to eat your plastic plumbing over this amount of time can’t be discounted.
Even stainless steel might be a worry. 316 is a good start, but all stainless steels depend on the chromium oxide layer, and permanently submerged SS is a significant risk. I have seen stress corrosion eat straight through 316.
Ground movement over time is guaranteed to stress your plumbing. Copper would be good but even it work hardens.
Keeping things clean is probably a key. No matter how well built you don’t want a fat burg clogging the works up over time. The London sewer system is probably the exemplar long lived system. They have all manner of unimaginably awful things to deal with.
Perhaps build the system with smooth bore and curves so that it is easy to send a cleaning pig right through regularly.
Don’t think this post wasn’t appreciated 