Plumbing and Heating Corrosion.   

 

Excessive ongoing radiator corrosion should not occur in a correctly installed system if? It is pre-commission cleansed and dosed with a suitable corrosion inhibitor. Routine chemical dosing does not mitigate the need for systems that will  simply retain water and exclude air. Many domestic heating systems in the Dublin area are fed directly from the main plumbing water storage tank. The pipe-work is permanent and is often found to have a failed non-return valve. This allows a two way exchange of water and results in corroded radiators. These systems cannot be dosed with a corrosion inhibitor or you could end up taking a bath in the stuff. I often have to re-arrange the fill point and pressure vessel of such systems before dosing with a cleaner, inhibitor, or sealer. See   Radtesting.com I used  Norstrom  Power flushing equipment for some years. I Also use used Fernox chemical products.

Newly built Dublin flats?    What appeared to be rust staining . This appeared to occur as the units were occupied A very common sight in the Dublin area.

Some recent Dublin developments have heating systems that are bound to self-destruct. Typically.     The plumber clears a small feed blockage and advises that he is unable to add corrosion inhibitor as the system's linked to the plumbing cold water storage tank. He tells them "ideally, a sealed system is fed from a separate feed/expansion, tank or the mains via an isolation hose,  remedial work is essential" Understandably there is disbelief.  The work is not done. Eventually the system has to be replaced long before the house is paid for. Boiler Servicing alone will certainly not guarantee trouble free heating. A sealed system may need a little water. An expansion vessel a little air. Or the system needs to be balanced. This is best done by someone with some understanding of the laws of physics. Essential missing components may have to be fitted. Like an additional expansion vessel. It is amazing how many people let the precious air out of a small  expansion vessel just to see if there is any in there. This is usually done by someone who does not have the means to put the air back in. Boiler manufacturers literature. Some Manufacturers of boilers with integral expansion vessels do not stress enough the possible need for additional expansion provision.

FERNOX WATER TEST KIT. Your plumber may carry out an on-site analysis of central heating system water. This is a check of major parameters affecting water quality. Determinations are of chloride, iron, hardness, pH, Fernox Protector A very basic test for the presence of dissolved copper is included. New Installations. The early detection of chlorides (flux residues) will allow intervention before corrosion occurs. This kit is relatively easy to use.

The Fernox water quality test.

Common Symptoms of Scale build up or Corrosion are.

1. The bottom or middle area of radiators remaining cold. (Partially blocked by sludge) 2. The need for frequent     venting of radiators. 3.Failure of circulating    pump to start readily. 4. Corrosion and oxide deposits    present in failed circulating pump

5. Water pitching from the vent pipe into the expansion tank when the system is in use. 6. Excessive nettling     or boiler noise. 7 Cracked boiler section and leakage.

Section of  3/4 flow pipe cut from a cracked cast iron back  boiler. It shows the build up that can occur with a direct system after some years.   The new found client splashed  around the kitchen muttering "I knew that dammed cylinder wasn't heating " Pic obtained by placing a short pipe section on the scanner

Traditional open vented type system.

A pitching open vent will cause corrosion which generates sludge. Some cases are due to most of the radiators in the house being turned off without pump performance or primary circulation being adjusted. This can result in water pitching from too low an open vent into the feed / expansion tank and gaining oxygen in the process.

General corrosion. Usually a fault is not discovered, if at all until the first radiator is blocked or corroded through. Sludge / lime-scale deposits may cause a cast iron boiler section to crack and leak At this late stage all radiators will have corroded to varying degrees and be partially blocked with iron oxide sludge the product of corrosion. Very little general corrosion produces a lot of sludge. Less than 10% loss of  steel thickness produces enough sludge  to cause cold spots on radiators. --------------------------------------Increasing the height of the open vent sufficiently has often solved the problem. Of course the open end is piped back down to just within the expansion tank. Your plumber may also consider relocating the pump.

Steam discharging from the open vent in the roof space has  condensed on the block-work behind the dry lining. It Appeared at all external windows,  door and vents and for years was mistakenly thought to be internal condensation. The entire structure behind the dry lining was saturated. The fact that there are hundreds of  houses in the development should not be lost on insurers. Perforated radiators are often replaced without ongoing corrosion being addressed.

The feed connection was almost completely blocked and only held together by hardened iron oxide deposit or rust.

Older gun-barrel pipe-work should certainly be checked out. Any feed-expansion pipe-work may be extensively corroded and partially blocked. Neglected pipe-work can easily become a horror story usually at 3am Is time for you to ask your local plumber to replace the feed expansion cistern and any steel pipes between it and the copper cylinder?

Your plumber will drain back suspect vent or feed-expansion pipe-work before tackling it.

Despite Recession or "Hard times" as Charles Dickens called it. Householders bear in mind the corrosion process goes on regardless. I cannot stress enough how important it is that any suspect pipe-work tank cylinder or boiler is examined by a competent plumber. This corroded fitting parted with incredible ease. Major property damage averted. only just.  Do splash out on a bit of essential maintenance before the pipes splash out on you. This advice is usually ignored so here's a link to a few independent loss assessors  Loss assessors

Sealed systems. NOTE. The air cushion of the pressure vessel compresses to receive expanded water when it is heated. Failure to maintain the air pressure will lead to leakage at radiator packing glands and /or safety valve discharge. Loss of pressure or too high a pressure, with or without system leakage, can be caused by a number of factors that a competent plumber will solve. I have used Flamco pressure reducing valves and found their performance consistent.) Set properly they should prevent the householder from over-pressurizing the system. Unfortunately it can slow down the filling process so the client may leave it open and connected. The isolation hose connection. The lever action valve would seem to be the best choice as it can be confirmed as being on or off at a glance. The pressure gauge should be clearly visible from the top up point. A heating system should not be permanently connected to the plumbing tank as it cannot be dosed with a corrosion inhibitor. Non-return valves can fail.

Proper hot flushing of flux residues from a new system followed by dosing with a suitable corrosion inhibitor should prevent electrolytic corrosion as shown above. A mild cleanser can be used before commissioning a new system. Hot water is more corrosive than cold. Just check the brass fittings for little white bits on the hot water / vent pipe as it leaves the top of your hot water cylinder. No they may not be bits of plaster left by the builders. It is probably the zinc leaving the brass fitting. This due to the electrolytic corrosion process. Don't try to remove it. The fitting will be porous and weakened.

The closing of  thermostatic radiator valves or zone valves can cause extreme pump pressures to build up. Extreme pressure differentials across the  system can allow ingress of air through micro-leaks. These leaks are almost impossible to find. A system may start to self destruct from the day it is commissioned. A self regulating pump or pressure differential by-pass valve ensures satisfactory operation, regardless of the  number of radiators or circuits used.  Ask your plumber.

Copper-clad steel ???

I have recently had to replace sections of perforated light gauge steel pipes, that had corroded externally. This copper coated material was stamped  "Steel tube Irish Standard" It looked like copper and was used with brass compression fittings.

Used during a copper shortage in the early seventies. Usually found in the floor beneath a weeping radiator valve..

Ensure that any seepages from packing glands are attended to as continued external wetting of this material will result in severe corrosion and perforation. In my opinion if such a system has been corroding internally or externally it is wise to re-pipe with copper. Just test with a magnet, if it attaches then the pipe's made of steel not copper. You may find a little magnetic badge shaped like a banana or an ironing board attached to the door of the fridge.

Do not push or scratch at minor weeps to see how bad they really are.  Be prepared to re-pipe. The heavier gauge black gun-barrel piping will also corrode externally if weeping packing glands are not attended to. Being thicker material gun-barrel will perform for many years if not used in damp conditions. Copper or stainless steel is perhaps the best choice for below ground mains to an external boiler-house.

"Well it did look like copper but was harder to bend" Copper-clad heating pipe-work is found mainly in the Dublin area.

This is a section of a 1/2 copper-clad steel pipe that was used for a below ground water supply to a house of flats. The thin external layer of copper protected it in the ground for twenty five to thirty years. Note the surviving inner layer of copper that has been squeezed in by the expansion of corroding steel. It was very quickly and carefully replaced. Trying to connect to a pipe like this means you could end up chasing it all the way back into the foundations of the building.

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Peglar Radiator valves. The Peglar radiator valve has two tiny rubber O ring seals, which can be simply replaced by your plumber. The sizes are coloured red or green. Tightening the nut on the spindle of this particular valve will not improve matters. I have found PTFE tape packed within  these valves, and this would be ok as long as the client is advised that this is only a temporary measure to stop leakage until the O rings are replaced. Of course your plumber is pleased to see a conventional packing gland nut this means a quarter to half turn clockwise does the job.

If a valve spindle is worn your plumber may switch the balancing valve cap and hand control knob around so that you will now use the other valve for on / off control. Poor quality radiator valves may weep regardless.

Micro-leaks. Miss-use of the parallel thread of a compression fitting may result in minor seepage .( signs of which are on this joint)  A joint like this on the return side could admit air into the system. A fillet of Fernox LS-X exterior leak sealer can be applied to such joints during the fault elimination process.

Below ground leakage.
How do I know there is below ground leakage.

Open System. There may be a continuous trickle from the ball valve without rise in the expansion tank water level. Or a drop in water level, with the ball valve temporarily tied up in the closed position. Sealed System. The system will quickly lose pressure when topped up. Note. A fully vented system with an air depleted expansion vessel will not hold pressure either and is often mistakenly thought to be leaking. If a pressure vessel is not maintained expanding water may seep from the system before the safety valve opens. I have replaced many below ground, corroded gun-barrel heating mains.  It is very difficult to completely protect them from moisture and surface water. All were replaced with stainless steel or copper.

The infrared thermometer shows hotspot in the concrete near a leaking heating pipe. Note the condensation around the edge of the mat-well. Hot water connected to and traveling up any suspect pipe can lead me to a leak. This is only one of many ways to locate a leak buried in concrete. Yes some builders are still burying pipes instead of putting them into accessible flooring or wall ducts. Some remove the lagging and pour floor leveling compound around the up-stands to radiators. This deprives the below floor pipes of space for. thermal movement. Leaks result.

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Chemical Cleaning.

Chemical cleaning is not for every plumber, it is most suited to the plumber with a natural curiosity, or interest in physics in the broadest sense of the word. In my opinion it is not for every client either. I only worked on badly corroded or neglected plumbing or heating systems when the clients fully understood their predicament and agreed that all work was done at the clients' risk.

Dissolving of sludge or scale may expose existing perforations in a heating system. Electrolytic corrosion may have caused brass compression fittings to become substantially weakened and porous. An experienced plumber will not knowingly expose his insurers to some of the unreasonable risks associated with badly neglected systems.

 

Plumbing corrosion.

This is a sample of a 15mm copper low pressure cold supply to a washing machine.
It was found to be perforated for the 4 meter section that ran with a 30 amp pvc
twin and earth cooker cable. (Between joists in a ceiling.)

(picture was obtained by laying the sample on scanner)

When I took the ceiling down it was leaking  like a urinal sparge pipe in a public house,
but as the pipe and cable parted company all signs of material waste and perforation reduced and  then ceased .

Was this due to the combination of a low flow rate and water remaining static in the pipe for long periods
 as would be the case with a washing machine supply and the presence of a field around the cable ?

What is interesting is that a 15mm copper hot water supply to the kitchen sink was in the
same situation but unaffected. (Hot water, high flow rate and frequent use?)
I think pinhole corrosion occurred where the condensation drips were on the surface of the colder copper pipe?

What do you think? I shall post opinions as the experts email them to me.

THE HOT WATER STORAGE CYLINDER. You will meet one and never forget.

It is not unheard of for a malleable iron fitting to be found corroding away in a cylinder. It should be made of brass unless it is part of the indirect heating circuit But if it looks rather a swollen rusty mass do not touch . Call your plumber. Usually found in a cylinder that was fitted at the same time as  G/B piped heating in the Dublin area.   Do not disturb until the water is carefully siphoned out.

A plumber should be careful. These can be very tricky situations as the corrosion will have expanded the female thread in the cylinder.   Easily separated from the cylinder with very gentle pressure. Just in time. Check the cold feed connection on your cylinder, Its usually hidden to the rear.

Some clients ignore repeated warnings about  risks, and insurers do not seem interested. Opinion or comment from insurers welcome.

It was alright before you touched it!

This fitting hidden to the rear of a copper cylinder surprised a young plumber who didn't realise he'd need a pair of wellington boots to change an immersion heater. A white or yellowish powdery surface deposit on a brass fitting is usually a sign of electrolytic corrosion. Corrosion of this cold feed connection at the base of the cylinder is often caused by residues from a corroding galvanized steel storage tank. (It leaves fittings porous and weakened) A small hand lamp and mirror is the best investment a plumber can make. Check both the tank and cylinder connections before working on either!

Mineral deposits found within the base of a perforated copper cylinder. Recently replaced.

I am told the green bits are probably the result of chlorides facilitating  pitting corrosion. Chloride increases the electrical conductivity of water and thus increases its corrosiveness.

Deposits removed to expose the full extent of pitting of the copper base. A Fernox lime scale preventer was immediately suspended within within the feed storage cistern. This will be replaced every six months or when reduced by 50% in volume. The camera was a Panasonic Lumix FZ 50 with Fujyama macro lens. settings F2.8 1/30 sec.

 

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