Good Lesson Learned Plumbing for Potable Water

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SmokeEater

SmokeEater

Feeling the Heat
Feb 10, 2011
358
Northeastern NY
I took this advice from both the forum(s) and my plumber brother that I could use black iron rather than copper, (next to silver and gold on Mendeleev's table) to save considerable money in pipe and fittings when plumbing up my "new" hydronic system. Did so, but since firing up in Feb of this year we have experienced a good and continuous amount of iron oxide in our DHW. This, as I now know, will continue until I "rip" out the black iron DHW loop and replace it with copper and fittings. There are 3 - 1 1/4" ball valves, a strainer, 2 threaded dielectric unions and a bunch of other "stuff" to modify or replace. Frankly, I knew of the iron oxide formation on the interior of the black iron, but didn't know it would continuously flake off into the supply. Thinking was that it would coat the pipe's interior and then remain there. Not so! I never saw a warning in the forums not to plumb this way for DHW, so I hope this thread will advise future DIYers and professionals (if they were still unaware) that to not use iron piping and fittings in the DHW loop. My fittings and pipe will arrive by UPS today and the bill for replacement parts, not counting labor (mine) and torch fuel, solder, and flux did cost in the neighborhood of $500. Wicked good lesson on Murphy's Law.
 
I have only used Black Iron pipe for gas or closed systems. Can not believe a plumber would suggest Black Iron pipe for any potable water use. Sure he did not mean Galvanized Iron pipe. In my system I use Pex for all plumbing that does not get over 180 degrees F.
 
I'm with maple1. You can mix copper and iron in a closed system (ie one with out oxygen).

Honestly I can't think of a situation where you would want to use iron pipe in DHW or any potable water system.

K
 
maple1 said:
I don't recall reading suggestions to plumb DHW with iron - only boiler loops? Could you do Pex any cheaper?
Click to expand...

I didn't research too much on the PEX except for some terminal fittings I would have needed for connecting to the indirect tank and the plate HX and they were pricey for 1 1/4" PEX, like near $30 per piece! Also, the rigid 1 1/4" PEX is pricey. Another reason I didn't go with PEX is because the normal crimping tools or clamping tools are not capable of connecting fittings to the larger PEX and so rental tools are needed and were $25 per day.
 
maple1 said:
I'd suspect if the question had been asked on here ahead of time, there would have been a resounding 'don't do it'.
Click to expand...
Maple, lesson well learned!
 
SmokeEater said:
I didn't research too much on the PEX except for some terminal fittings I would have needed for connecting to the indirect tank and the plate HX and they were pricey for 1 1/4" PEX, like near $30 per piece! Also, the rigid 1 1/4" PEX is pricey. Another reason I didn't go with PEX is because the normal crimping tools or clamping tools are not capable of connecting fittings to the larger PEX and so rental tools are needed and were $25 per day.
Click to expand...

But your DHW stuff wasn't 1 1/4 was it? All my DHW is piped 3/4", which is easy to work with in PEX or Copper.

K
 
Yes, I'm not sure why there would be 1 1/4" pipe in your DHW or potable water circuit - it should all be 3/4. Maybe there's more going on there that we could help you with?
 
kopeck said:
But your DHW stuff wasn't 1 1/4 was it? All my DHW is piped 3/4", which is easy to work with in PEX or Copper.

K
Click to expand...
Have a Smart 100 indirect tank that has 2 - 1/1/2" outlets and I heat my house and DHW with this tank. How I have it plumbed is that I have two boilers (independent of one another) connected to heat the Smart. I can use either one or two at the same time to heat the tank. Then I pump water from the tank with a stainless Grundfos thru a plate HX that has 1 1/4" inlets and outlets. I reduce the 1 1/2" tank outlets to 1 1/4", pump with a 1 1/4" pump thru the HX for the house and then return the cooler water to the tank. The plumbing is 1/1/4" to be able to move as much as 250,000 btu/hr when called for. The 1 1/4" hot supply has a T to 3/4" thru which I send hot water to the mixing valve and then to the house's DHW.
 
Doesn't the Smart tank have 3/4 in & out for the DHW?

EDIT: Reread your post - sounds like your using the Smart as a buffer tank, and not an indirect tank? Not quite understanding I guess, yet - almost sounds from what I read there that you're sending the same water to DHW as is heating the house?
 
Yeah, I'm confused too. I just downloaded the manual for the smart and the inlet/outlet for both the boiler and the DHW are 1 1/2 inch, which is just mind boggling to me. The thing can move 150 gallons per minute...wow.

None the less you are fine plumbing from your boiler(s) to the Smart with iron but the anything going in or out of the DHW ports shouldn't be iron.

So you must really have to neck that down to tie into your how water trunk right? My indirect hot water heater is piped 3/4 on everything and I can't run that thing out of hot water as long as I have a good supply of hot water from my tank (if a fire is going or my oil boiler is running it seems limitless)

K
 
SmokeEater tell us that the black iron is only on your boiler water side not the same DHW that you are drinking from?
 
DSC_0855.JPGDSC_0857.JPG unless you like repairs, copper brass or pex on any system. Sorry you found out the hard way. I know its cheaper, but I cringe everytime I see a multi thousand dollar boiler piped in with some black iron fittings and nipples. Kinda like putting walmart economy tires on your Ferrari.

I just did this repair last week, and that galvanized nipple was less than 4 years old, off a Madison Heights school boiler - closed loop system
 
Black iron pipe and fittings are perfectly fine for a closed hydronic heating system, most boilers are made out of mild steel anyway, what difference if the pipe is as well, although I have to admit copper makes for a much nicer looking job. Black iron cannot be used in systems with oxygenated water, this includes domestic water systems as above.
 
The heat exchanger would be the component used to seperate the domestic hot water (open loop) from the boiler and hydronic water (closed loop). Heat exchangers require two circulators to operate effectively. The stainless grundfoss would be used for pumping the domestic water through the heat exchanger. I hope you have at least two expansion tanks. One expansion tank for potable water on the dhw side and another expansion tank for the boiler and radiant side.
 
An expansion tank is required for domestic hot water if the system has no place to expand, i.e. there is a check valve or backflow preventer at the water meter or in the supply where expanding hot water has no where to go. It can cause a T&P to leak or faucets to prematurely fail or leak. Sure black iron may be acceptable, but when doing a good job why use it. Its a very common repair that can easily be avoided by using other materials. Even a closed loop system can have severe build up or erosion failures. Depending on water conditions its just a matter of when.
 
Black iron is preffered material for a boiler system with steel rads. Copper could cause dissimilar metal corrision
in the panels. Pex could blow out if over heated so I wouldn't have it near the boiler. Nothing wrong at all with black iron in a closed system with proper water and with air removel. Copper can fail just as fast or faster in the wrong situation. The ONLY advatage I see to copper is it is easier to install and may keep bacteria from growing in the water.
 
maple1 said:
But an expansion tank would not be required with a typical well & water tank - right?
Click to expand...

Maple,

As long as you dont have a check valve on the cold inlet to your DHW heater, you are OK. The expansion tank thats after your well pump will absorb most of the expansion of the system, assuming you are not operating right at your limit for pressure. As long as your pump/well tank is operating at the lower end, you do not require an additional expansion tank. If there is a check valve after this expansion tank, or if you were operating off of a municipal water supply, the expansion tank would be required.
 
Ouch!! That's learning the hard way.

To be clear on the subject of corrosion in piping systems. Black iron for any system that has fresh water going through it is a poor choice. Non-ferrous (copper) protected iron (galvanized) or synthetic (pex) are the choices available for domestic water supply. With the price of copper, I have seen a couple systems go in using galvy in the last couple years. (Old school still rocks) On the older dairy farms around here there are literally thousands of feet of galvy buried underground that have been in service for decades.

We even run into this type of corrosion on OWB's where the owner has neglected his water treatment program. In fact we replaced all the nipples and fittings on the back of an 8 year old OWB last fall. The system had been given it's annual dose of generic water treatment as recommended by the factory and it still corroded. The fittings collapsed under the pipe wrench. Even standard brass fittings (Chinese stuff) will corrode.
("dump in a gallon of this here miracle stuff and your system is safe forever") Riiiiight.
 
ALASKAPF185 said:
View attachment 64370View attachment 64371 unless you like repairs, copper brass or pex on any system. Sorry you found out the hard way. I know its cheaper, but I cringe everytime I see a multi thousand dollar boiler piped in with some black iron fittings and nipples. Kinda like putting walmart economy tires on your Ferrari.

I just did this repair last week, and that galvanized nipple was less than 4 years old, off a Madison Heights school boiler - closed loop system
Click to expand...

Galvinized should not be mixed with black iron in a closed system and is probably the cause of the corrosion.
 
maple1 said:
Doesn't the Smart tank have 3/4 in & out for the DHW?

EDIT: Reread your post - sounds like your using the Smart as a buffer tank, and not an indirect tank? Not quite understanding I guess, yet - almost sounds from what I read there that you're sending the same water to DHW as is heating the house?
Click to expand...
I am using the Smart as a buffer and a DHW tank, but the potable water doesn't heat the house, it exchanges heat with a loop that does heat the house,
 
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