Flushing pipes and cast iron baseboard

cwc

My boiler is 60+ years old and has cast iron baseboard in a closed monoflow system.
I had a contractor bring up flushing in the process of preparing a quote for a new boiler. I'm not replacing pipes or baseboard.
The system has not run for a month or more so I drained a glass of water from the system drain and it was perfectly clear. After an hour nothing settled out of it.
I then ran just the pump for an hour and repeated the test with the same results.
Is this a fair test?
How else would I determine a need to flush?

NY_Rob

Why wouldn't you want him to flush your CI baseboard as part of the new boiler install? Download the install manual for the new boiler and look at the "preparation" section... they will almost certainly mention flushing the spaceheating loops as part of the total install.

Proper flushing is not done using your circulator pump or by draining your system... it's done at higher velocity, higher volume and higher pressure which will be more effective at cleaning.

If you're replacing your old cast iron boiler with a MOD-CON then flushing is not optional it's 100% required along with a dirt strainer device.

cwc

NY_Rob said:

Why wouldn't you want him to flush your CI baseboard as part of the new boiler install? Download the install manual for the new boiler and look at the "preparation" section... they will almost certainly mention flushing the spaceheating loops as part of the total install.

Proper flushing is not done using your circulator pump or by draining your system... it's done at higher velocity, higher volume and higher pressure which will be more effective at cleaning.
.

Thanks for that info.

The reason I asked was that none of the manuals for the three boilers I've been quoted so far mention flushing and only one contractor mentioned it.

It was mentioned as an option that consisted of putting a Fernox product into the system and running the circulator for an hour or two. It added about 5% to the total system cost.

I was hoping there was a way to see if I really need to flush. If there wouldn't be a measurable improvement I don't want to have it done.

NY_Rob

Others will have to comment on the value of chemical treatments... sorry I can't help with that.

hot_rod

Yeah, it really depends on the condition of then old piping and components. The hydronic cleaner will certainly help clean up the piping, I would suggest flushing after the new boiler and parts are installed to get flux, pipe dope, oils, etc cleaned out.

You might also check the condition of the water that will fill the system. A simple TDS and ph test would tell you if the water you have on site is what the installation manual requires.

Here is an example from NTI