Xin Wei,
The risk scenario in more detail:
1. All plumbing is 'professional' grade (that is, at least double over-engineered), which means chance of spontaneous failure on the 10 year time scale is negligible.
2. The main risk of leakage comes from somebody falling and accidentally tugging on tubing. The chances that something would come apart are very small as there will be a lot of slack and everything is put together snugly, but we can tape over the barbed fittings to reduce this risk if that makes you feel more comfortable.
3. All piping will run along the walls far away from stray hands. Any piping that makes its way toward the middle of the room will drop straight down from the ceiling. Care will be take to minimize the number of barbed fittings close to electronics and to secure things such that tugging does not result in catastrophe.
4. Toby's boxes are extremely solid. They could probably support 6+ people standing on them and the rubber liner will last for decades.
5. The piano is more of a liability. Over-watering it in places will leak onto the floor due to the implementation being a bit shoddy. In the case of a freak electronics accident that results in enough power being sent to the solenoids to keep the valves open, a puddle could form and grow on the ground over the course of weeks (but remember, it's drip valves).
6. Pots fill up more quickly than boxes, so again, over weeks a puddle could form given an electronics accident.
A palatable security feature for conceivable accidents would be to install absorbent material under the piano and plant boxes so that a slow leak could be slowed down considerably. Preparing for a complete, fast unloading of the entire tank, such as the main outlet failing, is not feasible. The water will cover the entire floor of the room very quickly. This is why we bought an industrial tank and chose to use professional grade fittings. I will insure that a human is not capable of separating any of the joints before the flow-rate limiter. There is already a human-reachable master shutoff valve near the outlet.
So, I will buy some absorbent matting to place under all of the planters next time I'm at Home Depot. Let me know if you think that is sufficient, or if you think it is necessary to construct water-catches for certain worst-case scenarios[1].
Morgan
[1] Your idea for a catch under the 'boat' is fine, but let's forget about the inclined plank and just line the whole area with absorbent pads. If the leak is serious enough to be a problem, the plank will only temporarily divert the water. Creating a container-style water-catch is equivalent to putting a box within a box, in which case it would be more elegant to simply put each planter inside an enclosure! And from there, I'd rather use a box that doesn't leak in the first place rather than two boxes that
might leak. (Better to inscribe your data into a stone than rely on RAID 1: <
http://en.wikipedia.org/wiki/Standard_RAID_levels>.)
On Tue, Aug 24, 2010 at 1:49 PM, Sha Xin Wei
<shaxinwei@gmail.com> wrote:
JS had the same response. So let's take this fun, and important*, engineering exercise one more rev.
On 2010-08-23, at 3:21 AM, Morgan Sutherland wrote:
Hello Xin Wei,
(1) This will not leak with some probability estimate;
(2) When it leaks (and it will one day, from any number of places), the water will be contained or diverted from the electrical equipment, and the electrical cables in the room.
Chance of leaking is low due to low pressure and time-tested plumbing equipment. Formula for estimate:
P(Leak) = P(HumanError)
Therefore it will leak with P = 1.
We must assume that the system will leak (over the expected lifetime of the TML at least, and for good citizenship, of the EV building), and engineer a plan accommodating that eventuality. We must assume that the leak will happen when no one is around, and that it will leak when there is maximum water in the system (tank + pipes + bins), and when there are live power cables snaking over the floor because some student who never met you or any PLSS person years from now is rushing to finish an installation is jury-rigging power bc s/he blew some circuits on the wall far from the cistern, ...
You get the picture. My point is that infrastructure design (and yes, PLSS is an exercise in infrastructure design, for me) impacts those who will come after you, so you have to be concerned with people who will now know what you did or why, and who WILL do things that you do not approve, or even expect.
My raked floor idea may seem pie-in-the-sky, but on second thought, it may be feasible and easy. Just spit-balling here -- for example, when we put the boat back up, we could maybe place it over some board inclined toward the window, along which we'll place some catchment (or absorbent, not too flammable, material that also looks good and will not harbor pests). An aesthetic solution could be to place it over the "piano" table -- if we trust the table to do double duty, and have a way to failsafe the table.
Thinking further on the aesthetics -- maybe we could weave light sculptures into the boat or its rigging. Imagine phosphorescent or flourescent fabric "tendrils" twined with twine and pea tendrils.
The rolling carts, I hope, are engineered against accidents. The rubber material and its seals should be guaranteed by Toby to last say double the expected tenure of TML in that room. I.e. I would like a guarantee of 10 years :)
Xin Wei
Our version Long Now thinking will differ from utopianism in being concerned both with distant vision as well as the interim nitty gritty.
(3) The same for the "boat" which I absolutely adore and wish to see flying on and on. Assuming that the twine will break (and it will one day), what is the system for keeping the dirt from flying all over the place?
Due to massive bean death and spatial concerns, the 'boat' has been dropped to the floor for now. It may be resurrected in the future, but in a new form – reinforced++.
All piping is far from equipment and everything will terminate in a drip valve. The worst case scenario is a small puddle.
Where and how large will the puddle be if the full tank empties ?