Black Iron pipes - where to use??

[Corrado]

Hello
I was wondering if black Iron pipes should/could be used in shower applications with success?
I recently had a show installed and instead of using copper or brass the plumber used black Iron elbows.
Every morning when I start the shower up (with head removed) I get brown rusty water - often with sediment.
My plumber is adamant that this is not the reason for the rusty water but I have been told by others that the black iron elbows are the cause....
Who do I believe, there is sediment in the water so I dont want to block my shower head!
ideas MUCH appreciated!
Nick

 

[Bahco]

I personally would use 15mm copper pipe and fittings for a shower as I understand that the black iron pipe is more for commercial/ heavy use areas.
What size is the iron pipe?
I don't think your dirty water would come from the iron unless your hard/soft water is chemically reacting with it

 

[Igorian]

I asked this question when doing my NVQ plumbing course. Iron pipes tend to be used in areas where they may come under 'unusual' stress, such as in schools where the brats stand on them etc.

 

[Corrado]

I think he used 15mm black iron elbows.
any idea what else it could be then? The old pipes are copper and I didnt think that they would corrode. Could I be wrong? The water is reddish at start up and then eventually goes clear- there are also reddish flecks in the water that I assume would block the shower head in time... ?

 

[MANDATE]

If black iron elbows were used, Does this mean the pipe work was also in in black iron, because the elbows are threaded or is there some type of adaptor to change from iron to copper.
If the pipe work has been renewed and it meant draining the water tank it is highly likely that sediment has been disturbed and that is what you're seeing.
You could try taking the shower head off and running off some water from both cold and hot supply separately into a bowl to see which supply is causing the problem.
I can't see it being the elbows although I would prefer copper because they will not corrode, having said that the iron will last many many years.
I have iron elbows on my boiler which is just 31 years old.

 

[AdamW]

Perhaps this could be galvanic corrusion? I will explain:

Two different metals, when electrically connected (as they should be in a plumbing situation) and under water will cause one of the metals to corrode more quickly than it usually would and the other one more slowly.

This is the principle behind galvanisation. When your car bodywork is galvanised, they coat it with zinc. The zinc causes the iron to rust more slowly if the paintwork is scratched and the metal is exposed to water. The difference in "electrode potential" between zinc and iron is 0.32V. Which isn't a lot at all really.

However, the difference between iron and copper is 0.78V. Which means that the iron elbows will rust a lot more quickly than it would if you had all-iron pipework.

Basically, what I am saying is, putting copper and iron together in water (especially hard water) is not a good idea and will allow the iron to rust. However it wouldn't react so quickly as to build up so much sediment as you refer to.

 

[krispy]

Black iron will rust, hence the discolouration in the water. Wont be long before you see the leaks appear. If using iron fittings in this situation they must be pre galvanized, if so you should have no problems

 

[peter anderson]

what is the difference between black iron and low steel cast iron because low steel cast iron is routinely used to carry water underground?

 

[ChrisR]

"low steel cast iron "

No such thing exists old chap!
Ordinary steel like car bodies is iron with very little carbon in it.
Mild steel has a tiny bit more. Carbon steels , which are harder and heat treatable have a bit more . I expect pipes would be Mild steel.

Wrought iron is almost pure iron - not as good as it used to be. Cast iron is iron with LOADS of carbon in it - some are more malleable than others.

Black iron just means unplated.

I would not want iron elbows on copper pipes. It sounds very odd. Iron pipes are found in houses and they can cause staining, but I've never heard of just the joints - which as explained above would mean some kind of adaptor each side.

 

[peter anderson]

sorry, I meant low carbon steel not low steel cast iron. Low carbon steel is what they use to carry water underground isn't it. Copper is for above ground.

 

[AdamW]

That is probably because iron provides greater mechanical protection than copper. It is much harder to drill through an iron pipe by accident than a copper one.

Copper is more suited to domestic applications because it is easier to work with. Underground pipes last a long time and they can use heavy machinery doing it, so iron wouldn't be a hassle.

Don't they use plastic for underground water mains now?

 

[billy bob]

You do not use black iron fittings or pipe on water services, the only place black iron pipes and fitting are used is industrial and commercial heating systems and gas, you will get discolouration of the water, this is rust and is why you do not use black iron on water services, like it has been said galvanised pipes and fittings can be used for water services but this would normally be for industrial and commercial projects

Why did your plumber use these fittings

 

[AlanE]

Nick
Using black iron pipe and/or fittings on hot and cold water supplies contravenes the statutory requirements of the Water Supply (Water Fittings) Regulations 1999.
Ask for your money back and get an IoP Plumber in to fix it.
Tim (Reynolds)

(Copied from Institute of Plumbing site where this same question was asked)

Who do you want to beleive the experts or your plumber? Black iron fittings NOT suitable. WILL cause rusty water etc.

Alan