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.
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.