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Building a Dream



Pipes and Things

Throw out your Oakum
Toss out your lead

Make room for no hubs
and plastic instead

Remember your torque wrench
and pipe cutter too

Rough-in is easy
With ABS glue

Other than your electrician, no other tradesman will bore through your beautiful framing more than your plumber. He'll drill big holes through top plates, though floors, sills, walls, and any obstruction that gets in the way of proper venting, waste and supply lines. He’ll even char your two-by-fours as he uses his MAPP gas torch to sweat copper pipe.

ABS Plastic vs. Cast Iron

While plumbing costs vary significantly depending on the materials used, the most popular materials today for drain, waste and vent are ABS plastic and cast iron. Due to the ease of handling and lower cost installed cost, ABS plastic has generally replaced cast iron in most residential structures. However, compared to the old hub-type cast iron, newer hub-less cast iron has reduced labor costs making it more competitive. Advantages of plastic include its lower installed cost and resistance to chemicals and clogging, while advantages of cast iron include its proven long-term durability, fire resistance and sound deadening properties. Since some municipalities only allow cast iron, be sure to check with your building department during the design phase if you choose to use plastic.

Special Considerations

Whether you opt to use plastic or cast iron, each has their tradeoffs and considerations.  If not properly supported, long runs of plastic pipe can sag over time, creating low-spots prone to clogging. In addition, plastic pipe resonates more easily making it noisier than cast iron. If you want to economize on plumbing materials but plan to build a two-story house, use cast iron waste in any areas where the waste lines pass over, near, or through living areas. You'll be happier not listening to the sound of flushing water pass overhead.

Another area where I've noticed a definite difference between plastic and cast iron is in shower drain traps. In our house, we happen to have one of each type, due to a particularly tight fit we had in one bathroom. There is no question that the shower with the plastic trap makes a loud, resonant gurgling sound as the water drains from the shower, whereas the one with cast iron is notably quiet.

Cast iron is very durable and, if installed properly, should outlast the structure. It's also more durable when it comes to dates with the Roto-rooter. A vigorous snake has been known to crack or chew up the insides of plastic piping. Cast iron is also used underground, as it’s highly resistant to compression under the heavy loads of soil.

While plastic is quite resilient, it will have a tendency to compress under heavy loads, resulting in potential long-term failure if not properly protected. In general, plastic ABS pipe is guaranteed for 50 years and should provide satisfactory service if properly installed. Since cast iron has thicker walls and larger couplings than plastic, it's sometimes hard to fit it in tight spots. For short runs, DWV-grade copper can be used. Copper is a good conductor of heat, and some plumbers like to use it on runs that connect the kitchen sink/disposal to the main trunk. By flushing it periodically with boiling water, the pipe heats up which helps to facilitate the flow of oily deposits that accumulate from kitchen waste. The smooth interior surface of the copper also helps to prevent build-up from accumulating in the first place.

In general, waste pipe runs should be at a 1/4" per foot slope. More shallow slopes tend slow the movement of waste down the pipe while steeper slopes cause the liquid wastes to outrun the solid wastes, increasing the potential to clog.  Many a clogged pipe are simply due to improper pitch and support.

Water Supply Lines

In some parts of the country, water supply lines have turned to polybutylene plastic due to their relative economy and ease of installation compared to copper. Where copper is still required by local building codes, there are three grades from which to select: Type K, L, and M. Type M copper is an economy grade with relatively thin wall thickness. It is easily identified by its signature red labeling. While it’s accepted by most local codes for above-ground use, I prefer to specify type L for upscale custom projects, which is heavier duty and less likely to develop problems during service. Type L sports blue labeling along the length of the pipe. Type K copper, with its characteristic green labeling, is rarely used anymore except for some underground water service lines. Because the price is only about 20% more compared to type L, I like to use type K for underground use when I don't want to ever dig up the line again. Since typical underground runs in a typical suburban home are less than 50-100 feet to one hundred feet, it only costs an additional $75 or so to upgrade to type K. The thicker the copper, the more resistant it is to bursting during a freeze as well -- something even Californians get a taste of from time to time.

Sizing the Water Supply Line

How many times have you been taking a shower, only to have someone flush a toilet..and you nearly get scalded to death? This sudden change in water volume and pressure results from inadequately sized plumbing or insufficient water pressure. Some plumbers fail to take the time to thoroughly anticipate peak demand requirements, such as a shower, dishwasher, toilet and sprinkler system running simultaneously. In an age when water conservation is becoming more and more important, some erroneously equate big plumbing lines with water waste. Nothing could be further from the truth. Rather, the reason for using large supply lines is to provide enough reserve pressure and volume so that activation of a second water supply has minimal effect on the performance of the supply. The use of water restrictors is still a good idea for shower heads and faucets. But improper supply sizing for dishwashers, washing machines, irrigation systems, and toilets can result in water waste and appliances that operate inefficiently.

The larger the service pipe, the less friction loss there is which reduces volume and pressure. For example, you’re better off to use 1" sprinkler lines with 1" to 1/2" reducers at each head than to use 1/2" supply for all sprinklers combined. By using a 1" line, you can be assured that the last sprinkler on the line will have enough volume and pressure to function properly. It's amazing to me how many sprinkler systems are improperly engineered. As a result, brown spots can appear, or over-watering can occur. The trick is to find the right balance between cost of installation and function.

While each residential situation is different, I use the following rule of thumb for a typical 2-3 bath residence: provide a 1-1/4" supply from the street to the house. From there, use a "T" to provide a 1" supply for the sprinkler system and a 1" supply for the house line. Run a 1" supply to the first cold water fixture and begin to reduce from there. Also run 1" to the water heater, which, generally has a 3/4" output. Since most fixtures only require a 3/8" to 1/2" supply, using 3/4" pipe throughout guarantees plenty of water volume everywhere in the house.

After years of wondering why we had so little water volume, I found out that our standard 3/4" line from the street had been reduced to 5/8" at the meter. That made it tough to run sprinklers and showers simultaneously. Getting the city to change this is a big hassle, but it might be worth the time and expense if you want your water system engineered properly. Of course, the size of your plumbing supply must always meet minimum codes. Large homes with several bathrooms or a swimming pool may require larger supply lines for best efficiency.

Hot Water and Recirculating Loops

If you want to conserve water and desire the ultimate in instant hot water, consider installing a recirculating loop. In such a system, a water pump forces the hot water around your home in a complete loop that begins and ends at your water heater. While a recirculating loop eliminates the need to run a faucet for several seconds to get hot water, it nevertheless uses a considerable amount of electricity for the pump and gas or electricity to compensate for heat loss in the pipes as the water recirculates. A 24-hour pump can add $50-$100/year in additional electrical costs, not to mention the cost of the extra water heating required. If you operate on a fairly routine schedule, add a pump switch or timer that shuts off at night when you're asleep and during the day while you're away...and comes on just in time for the morning shower.

A high-quality recirculating pump, such as a Grundfos, runs a few hundred dollars installed. An available thermostat and integral timer makes this a favorite choice of homeowners. Be sure to provide unions, a shutoff valve, and check valve as part of the assembly, following carefully the instructions that come with the pump.

Instant On-Demand Hot Water Heaters

There has been recent interest in on-demand water heaters that provide an endless supply of hot water. There are several manufacturers of such systems. Advantages of on demand heaters include very high efficiency (you only heat the water you use) and small, compact size. Available in both gas and electric versions, on demand heaters are a good alternative to traditional tank type heaters, particularly at the end of a long run or in a remote location, such as an in-law guest house.

The key drawback of most on demand heaters is their inability to provide sufficient hot water during certain peak demand times. Depending on the incoming water temperature and the desired hot water temperature, on demand heaters may have trouble keeping up with two showers running concurrently...and a washing machine filling up. Typically, on demand heaters can provide 2-4 GPM of hot water. Anything in excess of this will result in lower desired temperatures. Before installing such a system, calculate your expected peak usage and be certain that the system is capable of delivering sustained hot water under loaded conditions. For reference, typical incoming ground water temperatures are approximately 50-55 degrees F in North America.

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