Yellow Tint in Hotwater

Check Cause `Yellow Water`` due Low Ph

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Galvanized steel. Could the zinc coating be gone? Letting the steel rust. Could that also account for the iron particles. If the pipes are threaded together the threads are usually not coated. If the pH is wrong this could lead to degradation of the system.

I lived in an old house that used galvanized steel if the water was not used for a few hours as soon as a tap was turn on the water ran from red to yellow to clear. And the faucet screens needed to be cleaned every so often from iron particles. It was worse after working on it or if the system was shut down for a period of time.

Let us know what you find and how you fixed it.

The Galvanized Pipe

The threads on a galvanized pipe are cut after the galvanizing; therefore materials exposed to the threads and especially the end of the pipe where it was reamed to remove the cutting burr starts to rust as soon as it is exposed to water. In a few days it will be staining. After a short time the rust will migrate under the galvanizing and create much more rust, so much so that it will eventually significantly reduce the effective i.d. of the pipe if not completely block it altogether.

Get rid of the galvanized pipe altogether and flush the other piping completely with multiple rinses of extended time. Install some other suitable pipe such as copper, St Stl, CPVC, etc. and your rust problems should be gone unless you have residual rust particles stuck in the other piping. If so try to mechanically clean the suspect areas.

As a note- galvanized pipes are galvanized before the threads are cut, true rigid conduit piping is galvanized after the threads are cut. If conduit is field cut it must be cleaned and the threads re-coated with several layers of cold galvanizing spray.

Good Luck, Old Salt

How old is your hot water heater? If is old enough to NOT have some sort of plastic inner liner, then there is a good chance the color is coming from inside the water heater itself. And, if that is the case, it is just a matter of time before the bottom rusts out, and you have a flood.

I now of electrochemical effects which could cause dissolution of iron from the stainless steel vessel. The copper is higher in the electrochemical scale then iron and is the reason.

You could replace all Copper with SS or you could also try to insulate all copper tubes from all SS parts, which is as hard as replacement. Insulation must prevent electrons flowing from SS to Copper, which would mean to e.g. insulate all Copper pipes at all possible contact spots, also supports which may have a connection to ground.

What about a Zinc sacrificial anode inside the Calorifier? This anode would be lower in potential than copper and SS and would get dissolved and, of course must me checked and replaced after some years.

Have you got a recirculating pump to keep the water at the tap instantly if so check the pump is a bronze one otherwise it could be the impeller causing this, I've had it once and changing the pump fixed it.

It seem the vessel is the ship,you could have cleaned the fresh water tanks but are your tanks properly coated? If not you need to do that.Mean while fill up tanks at least to maximum,and top up when tank level is 80% full. In order to minimise oxidation on bare steel surface plates and free surface effect, ship rolling in rough weather,low water levels in the tank will act as cocktail shaker on rusty tank surfaces.

Without visually checking out your entire hot water system I can only make some educated guesses base on the info you provided. If all of your dissimilar piping is galvanically isolated from each other then i would suspect your hot water heater and would replace it with a new system (maybe go tankless if possible - less energy waste, less weight, less space). If you can see ALL of the hot water piping and the dissimilar materials are not all isolated, install isolation unions at these joints. Plan B would be to re-pipe with a single material. For durability and/or any exposure to sunlight/UV rays suggest rigid copper pipe (SS works as well but more expensive in material and installation). If there is no exposure to sun/UV rays AND no risk of mechanical abrasion then I would consider PEX pipe with slip on removable fittings. Easy to install and if necessary the fittings can be removed and reinstalled.

It's most certainly the hot water tank. I had this issue a few months ago. It's rust from within the tank. If you want to double check you can disconnect the pipe from the lower part of the hot water tank and let the water out. You will see not yellow but brown water (even a tinge of red) coming out. If that is the case, change the tank and do not drink using hot water.

When our plumber changed the tank, all was perfect. He also recommended that once a month to pay a visit to the hot water tank and pull the pressure release valve for a few seconds. This will help make the tank last longer from corrosion as there will be less pressurized air inside the tank.

Thank you all.

I have taken all your inputs and I will definitely update you all on our findings.

It understand that the dissimilar metal piping not insulated from each other.Will do this first.Also regarding the circulation pump impeller material I have to check, as when the circulation pump is closed the yellowish color is less dense.Of cause this is in a ship.Also there is a complaint that some skin irritation/rashes due to this.We are going to dismantle the piping to inspect the damage.According to all you generous inputs, It can be a contribution of all above stated. I will keep you apprised.

Jayan: Have you ever checked out the water source? Organic content of water can keep iron in solution and force a color (yellow) when it is heated. The iron will not come out of solution due to the complexing between the iron and the organic material. It happens a lot in ground water. You may have multiple sources of water and I am not sure of the treatment provided by the ship. Is it capable or robust enough to treat multiple sources or is it designed for a single source? The only way to check out this type of complexing is do have a lab prefrom total iron as well as dissolved iron on the cold water supply. Total iron will require a digestion at the lab to force the iron out of the complex. You should also know the total organic content (TOC), pH, Langlier's index (calculation for hot and cold), color, and turbidity. The cold water can look very different.

That being said the galvanic cell potential may be very high and you may see deterioration of plumbing from this source. I just wanted you to be aware of the potential for the raw water to be a source of chemically induced color when heated.