ᐅ Yellowish-brown water coming from the tap...

Good day!

Yesterday, I removed my 26-year-old dishwasher because a new one is being installed today. Beforehand, I turned off the main water supply as a precaution and drained the remaining water from the lowest outlet point. I wasn’t sure if the shut-off valve was completely tight.

I then screwed on a blank cap and sealed it with Teflon tape, just to be safe. When I reopened the two main valves, yellow-brown water came out of all the taps on every floor.

The situation cleared up quickly, but I’m still wondering: where did that water come from? It seems that by shutting off and draining the system, I mobilized some stagnant water that had been sitting there for a long time and was now released. I tend to think it originated from the hot water side.

The house is as old as the dishwasher.

Does anyone have an idea? Many thanks!

Do you have an unused circulation pipe?

No, definitely not. It was not necessary and therefore was not built.

These are probably deposits from old galvanized water pipes that have come loose. Try unscrewing the aerators on the faucets to see if any particles have settled there.

I recently checked all the aerators; they were clean. By the way, there are no galvanized pipes anywhere—everything is copper.

I’m wondering whether it is possible and practical to descale the entire piping system after 26 years, including the heat exchanger in the boiler. Some time ago, I tried to drain the whole system and add descaling solution at the highest point near the shower, but I was unsuccessful...

Normally, copper pipes develop a so-called protective layer on the inside over time, and this should be preserved.
If you ask your water supplier, they can provide information about the quality and characteristics of your drinking water, so that appropriate measures can be taken if necessary.
Under no circumstances should anything be added to the drinking water pipes, as this is not only prohibited but can also cause long-term damage to your pipes.