Descaling?

Background: So I lost 1 of 2 water heaters 2 weeks ago. And then yesterday the other one went.

They made it 22 years, but gave up the ghost at almost exactly the same time.

After the first one left, we couldn't turn of the water because none of the valves shut completely. Called some plumbers, got totally ripped off, but they drained the system and serviced the valves.

when we pulled out the old heater, I noticed the lines were about 50% blocked with gunk and draining the heater was pure sludge for the first minute. This surly explains some of the hot water pressure problem we were having on higher floors.

Well now that we are without hot water in any part of the house, replacing those heaters has become a priority.

Question:

I was wondering if it would be worth it to try and descale the hot water system? Plumbing is all copper ("L"). I obviously don't want to dissolve the pipes with acid but there is a descaling solution for sale at the hardware store that says it's safe for copper pipes. The instructions say: drain the system, fill it up with the solution, let sit for 3-5 hours, flush. Repeat if necessary. Would you do this if you were me?

Water pipes are gravity pressurized so wouldn't need to pump the solution into the pipes.

 

If it makes a difference the crap in the pipes appears to be more iron then whatever the white scale is though there is some of that too. I'm guessing a lot of it comes from the centuries old infrastructure here rather than the source since it's mostly river water.

 

The sludge you saw may may been localized at the water heater, and unless you have a major mineral buildup, I would be disinclined to descale copper water piping.

In contact with most drinking water supplies, copper develops a protective layer of copper oxides and copper carbonates on the inside of the pipe. If you were to descale, it would develop the protective layer again over time.

Since your water heaters lasted 22 years, I would guess you've got pretty good water. If it were my house, I'd flush with water until it ran clear.

 

Thanks. I'll try flushing first. I took a look at the connection to water heater I disconnected and the straight section is relatively clear, compared the the obstruction at the elbow. The crud there took the form of sort of large long chunks.

According to the water utility, the water is hardness is 73mg/L at the plants, and 98mg/l averaged among end user samples.

I don't know if hardness is the right measure though. There is something that precipitates out and forms a layer of decently thick orange sludge in the fresh water tanks which get washed out once a year. I'm guessing that is the same stuff that ends up in the bottom of the water heaters as well.

 

Orange would usually indicate rust, from galvanized piping or possibly 22 year old water heaters.