Plumbing – Descale municipal water supply line

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I have a pretty old house (1910) and the water supply line from the street is ancient. I suspect it may be narrowed with scale, and/or manganese fouling (there is manganese in the local supply), because the water pressure, while ok, is not that great.

At one point the town offered to replace old supply lines for free, but now they tell residents to get a private contractor. Digging up the line is a big deal because it goes down into the foundation before heading out to the street, so it must be at least 6 feet deep.

I am wondering if an easier route might be to descale the line somehow, either with a snake/rooter or by a chemical method.

Note that there does not appear to be a curb stop on the line and the meter is located in the basement.

Best Answer

Are you sure its a scale build-up. Just a few things to note.

Here is just a shortlist of things to try first:

  • Make sure that your water meter is not the cause. there is a filter in most meters, and it is prone to build up with gravel and small stones, The filter is on the meter on the inlet pipe side, but you may need the munic to do it for you.
  • One possibility is that the towns pressure has decreased due to more consumption, that may be the cause of your pressure loss.
  • Obviously look at all the gause filters on taps and check they are clean (i am sure this has been tried already)
  • Generally, Scale and sediment are more prone to build up on joints and T's, rather than the straight sections, one method is to try to locate the joints and have someone replace just those for you.
  • See if you can locate your curb stop (shut off valve) and increase flow slightly

Scale build-up will occur where there is a rapid change in pressure or temparature (water heaters specifically), however, in your case any reduction valves or joints would be the first place to look.

There are actually many types of scale, and the removal technique should be suited to the type of scale, A Poor choice of removal method may actually promote rapid recurrence of scale. Scale Strength (Delicate, brittle, whiskers, crystal, rock like) , texture and purity (one mineral or multi-mineral) are all determining factors

  • Carbonate minerals are highly soluble in Hydrochloric acid
  • Hard Sulfate Scale more difficult since it has a low acid solubility (need chelating agents)

The common way to clean scale of the pipes is an acid wash, sulfuric or hydrochloric acid is normally used, whereby the pipe is opened up just after the meter, and connected to a pump, then one tap is opened at the end of the line, and a bucket is placed, then the pump circulates acid through the pipe and flushes the system. The problem with this process is that the acid does etch the pipe and create craters for accelerated scale build-up in the future. The system must be flushed extremely well, since the spent acid solutions of scale are excellent incubators of fresh scale.

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