September 2006 - Under Pressure

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             Although the title of this letter could be taken to (always) refer to its author when the printing deadline is expiring, that’s not the intended meaning this time. We’re referring now to a physical characteristic of water in pipes. Pressure is what makes piped-in water more convenient than water carried from the creek in a bucket. Lack of pressure makes people who have forgotten about the bucket system grumpy, but so does too much pressure. On this water system, you could be exposed to both problems - but not simultaneously.

             If you emigrated from some flat place, such as Garden City, Kansas, you may wonder why our system pressure is not maintained at a uniform 60 psi (pounds per square inch), like it was back home. Well, it’s because of the terrain. The average slope in the USCDWUA service territory is 5% toward the south-southwest. Five percent means that for every mile southward, the ground drops 264 feet vertically. This 264 vertical feet of water creates 115 psi of pressure. So, at the end of each mile of south-going pipeline, the pressure is 115 psi higher than it was one mile north. If this process were allowed to continue unchecked, the pressure at the lowest point on our system would exceed 800 psi. While such pressure might be useful for removing paint from your siding, it’s not really practical in the household. And it’s a bit high for common pipeline materials, which are happiest below 200 psi. So, to control the effect of gravity and minimize explosions, we employ pressure regulators (37 at last count), located at different points on the system where the pressure needs to be reduced.

             Although a “safe level” for the main lines might mean anything up to 200* psi, it might not be a safe level for your home. Therefore, you need to have a pressure regulator installed in your plumbing, before any appliances or fixtures. If you don’t know whether you have one, you should find out. Regulators have a finite operating life, ranging from 10-15 years for a good quality ($80) model to maybe two days for junky types often found for less money. If your pressure regulator is failing, the first sign may be a leak from the pressure relief valve on your water heater. Some people mistakenly replace the relief valve, which was only doing its job, and this does not solve the problem, of course. In some cases, even correcting the pressure does not cure a leak from the water heater relief valve. That could mean a thermal expansion tank is needed to allow heated water to expand safely rather than forcing its way out through the relief valve. Consult a plumber about this.

             On the other hand, there’s low pressure. Low “pressure” is often a synonym for low flow. If your house plumbing is restricted by undersized pipes, encrustation of rust, clogged strainers, or the presence of Satan-designed congressionally-mandated “water-conserving” fixtures, the root cause is not really pressure, but the inability of the plumbing to deliver. You might improve things marginally by increasing the pressure at your regulator, but it would be better to find out if you have a restriction in your plumbing and fix that first. It is also possible that you live at a point on the system where there is no more pressure to be had. We would prefer that there were no such places, but this ain’t Kansas, and we can’t pretend to have a level playing field. We try to maintain at least 50 psi at all taps, but it’s sometimes impossible.

             We welcome your complaints about low/high water pressure. (Hah!) No, actually your feedback is the best way for us to find out what is really going on with the system, and where we need to make improvements if improvements can be made. If you’re just plain outta luck, we’ll cheerfully tell you that, too.


*Rumors of places where the pressure exceeds 200 psi are true. That’s how we get water from the valley to the hilltop without pumps.

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