Low water pressure in a home can have numerous, sometimes combined causes. Leaking pipes, a heavy demand on a shared service, altitude, closed valves, and faulty outlets are all potential causes. However, one of the major causes, and one that impairs the pressure throughout an entire system, is corrosion and blockage in the home’s water service line (the pipe connecting the municipal water supply to the home’s water system). Moreover, corrosion can also lead to piping leaks, especially in hot water pipes and at points of vulnerability, such as threads, when the pipe walls are thinnest.
In Toronto, the age of much of the plumbing infrastructure means that homes’ water service lines were installed as either lead pipe (which merits its own replacement for health reasons) or as galvanized iron pipe. Iron pipe of this sort is susceptible to rusting on its interior wall, and when it does so water pressure can be restricted, sometimes significantly.
As the water service line is the point through which all water entering the house must flow, ensuring it is not a restriction on flow is crucial. This piping running from the city property line to the house (and water meter) is the first priority. In addition, the meter itself can be a limiting element. The most important consideration for ensuring good water pressure is therefore the diameter of the water supply line, and the pass-through diameter of the water meter that is inline with this pipe. Older installations often have 0.75″ inside diameter pipes and corresponding 0.75″ diameter connections on their water meters.
How important is diameter? The diagram below compares a 1″ diameter supply pipe with a 3/4″ diameter supply pipe. As you can see, the 3/4″ pipe has just 56% the cross-sectional diameter of the 1″ pipe.
But that’s not the usual reality for those with old pipes: if they are galvanized iron, then corrosion can decrease diameter; and in Toronto calcification can also be a factor. The average hardness for Toronto water is 124 milligrams of calcium carbonate per litre. This is considered to be moderately hard, and the average water PH is 7.7, so over time calcium deposits can also affect pipe diameter.
When a 3/4″ pipe has 1/8″ of rust and calcium impediment on its inner wall, it effectively becomes a 1/2″ pipe. As shown below, this pipe is now capable of carrying less than 25% of the water that can pass through a 1″ diameter pipe. It’s now easy to see the constriction that will occur.
The best solution is replacing any service piping having less than a 1″ inside diameter with a new 1″ diameter service line and complementary meter when undertaking upgrades to replace lead service piping or when you have a galvanized iron intake line and chronically low water pressure.
The City of Toronto does not provide assistance to upgrade service piping for the sole purpose of increasing water pressure (unlike the help provided with with other specific plumbing upgrades, such as installing a backflow prevention valve or removing lead service pipe). The City of Toronto will however schedule a free water flow test if you are experiencing chronically low pressure or have experienced a sudden drop in pressure. To qualify for a flow test your home:
- must have a water meter (some Toronto homes don’t);
- must have a copper water service line from the city main to the water meter; and
- must have an operable stop and waste valve that is not defective
The City considers a flow rate of seven litres or less per minute to be low water pressure qualifying for rectifying.
Note the requirement that the water service line be made of copper up to the water meter: this means that the free flow testing offered by the City will not be of use in determining whether you have a flow problem if your service line is lead or galvanized iron: such service lines will need to be replaced first, before testing. Replacing lead service piping can be assisted by a City of Toronto subsidy, but if you suspect your galvanized iron intake is the source of low pressure you are on your own until it is replaced. After replacing galvanized iron intake lines, you can then apply for a free flow test.
If after ensuring that your service line and water meter are not causes of low water pressure and you still have low pressure, it’s time to look at the remainder of the system. When it comes to piping, the worst places tend to be pipe elbows, pipe in the lowest points in the house (basement), and horizontal runs of piping. But discussion of those upgrades is for another time.
If you are interested in replacing galvanized iron piping or in enlarging your water service line, contact Master Drain for more information. Properly flowing water makes showers and general water use a pleasure; poor water flow is a great frustration.
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