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Question DetailsAsked on 1/9/2018

What is the best way to remove all brown sediment in cold water lines after a water main shutoff and turn-on?

We recently had our water heater replaced, requiring the water main into our home to be shut off. Following the work, we have experienced much brown sediment coming in to all cold water lines, into all toilets and tanks, faucets, showers, the dishwasher (we suspect), and the washing machine. It has not stopped or reduced in volume going on three months now. We continue to clean the faucet and shower filters as best and often as we can, including for the washing machine. We would very much appreciate advice on how best to clear all these lines of sediment. What are our best options, and the possible cost to do so if expert help is required? Thank you!

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Realizing you are probably already using water by now so some steps may not be possible before sediment gets into them. Read all the way through before starting - especially if hot water has already been used so grit is coming out hot pipes too - see 10) below on that.


Do not use washer, dishwasher, bypass (or shut off if not in-line on main line) any water softening/filtration system, and do not use any other water-using appliance or hot water any more till the cold lines are cleaned, to keep as much sediment out of them as possible. Turn boiler or tankless heater off or to pilot (to prevent overheating a possibly not full tank) and shut off incoming water supply to it if feasible to prevent it from drawing the contaminated water.


The following steps (do in order) are predominately for "solid" sediment - that which feels "gritty" or "sandy". If you are getting slime or oozy, soft material that is commonly bacterial (commonly iron eating bacteria) in nature, especially if black/gray/blue, which commonly needs a chlorine or similar chemical treatment by a plumber to kill it off and clear it out.


1) if you have outdoor hose bibs on the line or a low-point drain valve (commonly right after the main shutoff valve), especially early on in the piping after the shutoff valve, open those first (full open) to get as much of the sediment out of that part of the piping before running other water - because running the other faucets (which are normally higher up) initially will move more sediment toward them, and may not clear out heavy sediment like rust or sand as the pipes go vertical. With them full open (discharging water at a harmless place away from the foundation), shut off and reopen the main shutoff valve several times and let the water drain back out of the pipes to those drains - this filling and emptying (the same process that caused this problem) will loosen up remaining sediment more and hopefully free up almost all the material which might break loose again in short order during normal use. 


Sometimes this step along is sufficent - but probably 3 times out of 4 or so, not so much. 


2) go around, after removing filters/screens/aerators on the faucets (to extent you can do so without damaging them), opening all faucets and hose bibs (avoiding foundation flooding - use hoses), on full COLD only, keeping an eye on drains and especially on the lowest level drain in the house (including any floor drains) in house just in case a drain or sewer line is restricted and cannot handle the flow - but in all but pretty significantly partially blocked lines that should not be a problem. For shower-tubs run into tub,not through shower head, for greater flow. 


The idea is to get the maximum flow rate through the piping to mobilie and flush out the sediment. This much greater than normal usage flow rates will remove everything that mobilizes at that flow velocity - so whatever does not move also should not move in noticeable quantities during normal household usage. Let it run several minutes, flushing all toilets a couple of times too to increase water flow. Then go around from faucet to faucet, using a white paper towel or clean white bucket or clear thin (like soda 2 liter) bottle to catch some water to see if it is still coming out dirty or not (thoroughly cleaned and destained white bucket like old drywall compound pail is better - will show both grit and discoloration better than plastic bottle, where grit on the bottom can be hard to distinguish because the plastic is thicker there). 


Some people also open and close the incoming main water shutoff valve during this time, to loosen up any other sediment in the pipes by varying the pressure in the pipes - while the facuets are all open.


3) then, progressively from the water source (where it comes into the house) on towards the further "downflow" faucets, start shutting off the faucets once the water is coming through clean there. When you come to the water softener or filtration unit, which would commonly be one of the first taps along the way, shut off the bypass and let it flow normally through that unit too.


4) If you have been using water and have a water softener or filter unit, any initial filtration filter may have to be changed out at this point. Also, the unit should be cycled (refresh or recharge cycle) before continuing on to further points.


5) if you have any non-bladder type pressure tank on the cold system (usually only with well or surface-fed supply - commonly looks a lot like a water softener tank or water heater) that should be flushed out as you get to it along the lines


6) working along, shut off faucets one by one. This process will then have cleaned all the branches to the faucets at maximum flow rate possible without outside help


7) then, go back to all faucets where clean water is important (so maybe not hose bibs outside) and individually (one by one) open each one full open on cold till water runs clean, then shut off and go to next one. The previous step cleared the branch pipes as much as possible - this step, because the pressure will now be greater at each faucet with all other faucets closed, so run enough water to clear the feed lines to that point of use, till it flows clear. Replace screens or faucet filters at each as you go. 


If you have screens/filters/aerators at faucets which you were not able to remove initially before the cleaning, at this point you will see if they are blocked and really need to be removed or can stay with some grit in them. Commonly, using a mirror and flashlight you can look up into it an see if it is clogged or not also.


8) this should then have moved as much loose material through as you can do by this method. Last things to open back up to water usage are point-of-use filtration units (like under-sink units or screw-on ones, which likely need their filters/elements replaced if you have been using water. 


9) then open the drain on the water heater and drain out a tankfull using a hose (with inlet valve and drain valve fully open) to get the sediment out of the bottom of the heater - much of the physical grit type will have accumulated in the heater and not passed through into the hot water lines - that is why step 2) used COLD water only, to keep from flushing sediment into the hot lines during the initial flushing process.


10) then go through the same faucet opening routine with all faucets turned to only HOT water on to flush the hot lines - till each one runs clean. If no hot water has been used since the shutdown, this may no result in any dirt coming out - or if the particles are just solid rust or sand may not have made it through the water heater, so hot pipes may be pretty or fully clean. Even so, since the water heater traps most of the heavy particles, usually the hot lines will only be dirty if your problem is bacterial growth (which is normal in pipes, especially in metal piping).


NOTE: If water has been used since the shutoff and before cleaning, then in step 2) both hot and cold can be opened at the same time and skip 10), which will actually run more water through the cold pipes up to the water heater takeoff and clean that part better - though that is commonly not far from the incoming cold water supply pipe so normally makes little difference.


11) then, once you have clean water running through the pipes, run a load or two in the dishwasher and clothes washer of things that do not matter, with normal soap - not anything that can stain. Not good for the clothes washer to run empty - so some old towels or outdoor work clothes or such should be in it. Run full permanent press cycle so both hot and cold water are used in the washer.


If they have been used since the turnoff, you may have to turn off the shutoff valves to them and remove the supply hoses to clean out the inlet screen usually found in the hose inlet fitting.


12) if if has been a day or few since this occurred and they have been used, whether you have to drain and flush any tankless water heater or boiler is a tough call. Certainly, if there there is a low-point drain valve on the tankless heater, drawing off some water at full open on the valve (be careful - especially if this is high-temp combined heating/domestic use heater) to clear out the sediment in the tank would be a very good idea. If it is near time to chemically clean it (periodic lime removal cycle) this would be a very good time to do that.


Boiler for steam/hydronic heating system should be flushed for at least 5 gallons or so, from its low-point drain, if feasible - but unless the sediment is pretty heavy in the water you probalby did not get a lot in there because only small amounts of makeup water go in there (assuming we are talking dedicated, not combined system), so waiting till spring/summer to do an annual flush (as part of normal maintenance) should not be a big risk. If you have a combined heating/domestic hot water system, then the boiler and the storage tank should be flushed if much of the dirty water was run.

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If that does not do it, then sometimes compressed air (at a low enough pressure to not overpressure the pipes) has to be introduced just after the main shutoff valve and allowed to bubble through the piping with water flow on to clear the sediment. This actually works a LOT better than just running faucet water, but costs a couple hundreds more too.


One thought - if you have been having this for 3 months, then you had a LOT of crud in the lines - either from accumulation over the years, or your lines are corroding pretty badly - so before paying for a thorough flushing (unless you do that yourself) you should probably have them opened up a couple of convenient places and looked at for corrosion and mineal/algae buildup. Your plumbing, especially if over about 50 years old (as little as 20-25 with aggressive water, sometimes 60-100+ with non-aggressive water or pipes like asbestos or pure lead - though of course those have their own problems), might be near its life and you might be looking at a possible replacement job.


Also, after a lot of crud breaks free like this, and especially if a chemical cleaning or chlorine bacterial growth kill is done, with older or corroded lines you have a significantly elevated risk of leaks afterwards so pay attention to possible leaks, and periodically (when there is no water being run) put your ear to any water supply pipe or faucet and listen to hear if you can hear a leak. Bear in mind fans and any heating system pump has to be off, and commonly you can clearly hear the burners in heaters, so you sort of have to listen NOW, beforehand, for what is "normal" so you can compare after any aggressive cleaning. This increased risk is because the cleaning remove the built-up bacterial growth or mineral coating, exposing possibly corroded pipe underneath with was not leaking because of the covering growth or mineralization or rust.


Just flushing the lines per 1) through 12) above should not dramatically increase your leakage risks unless your pipes are about shot anyway.


Cost - depends on labor charges (from about $75-150/hr in most areas, up to $200-300/hr for a plumber in a very few high-cost metro areas) - but commonly 2-5 manhours flushing with running water only, more like 3-6 manhours with compressed air for a normal sized house, so you are talking on the order of $500 plus or minus a hundred or two in most cases. So - going through the flushing sequence yourself, if you are a bit home-handy, to see if that works for you, might be a good start - though with the 3-month thing, since you said MUCH brown sediment, I am thinking you may well be looking at more than just a minimal flushing job here.

Answered 10 months ago by LCD




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