Skimming multiple times

JodiMe

Two winters ago (about a year and a half ago), we had quite a bit of system work done (multiple valves and a radiator replaced). The tech skimmed the boiler before leaving and, s I expected, it had to be done again a couple weeks later (symptom: water hammer).

We ran our system for a couple weeks last year before the hammer started again, skimmed again and rinse, repeat. We skimmed 2-3 times last winter season.

We have been running the heat for a few weeks now and the hammer started up again. It’s currently skimming as I type this, and I see a thin slick on the water.

My question is, how many times do you think we will have to do the skim?

The boiler was new when we moved in (converted from oil to gas per real estate contract), so I guess that could also contribute to the oil, right?

Just curious if we should just get used to doing this a couple times a season or if it’ll just finally be “clean” one day.

Thanks in advance.

KC_Jones

If memory serves I did roughly 12 hours of skimming when I replaced my boiler. Mileage may vary.

I also did a "wand wash" before doing the skimming.

BobC

Exactly how are you skimming? Show us a picture of the boiler and identify where your skimming from.

It should take several hours to fill a 5 gallon bucket unless you can skim through a cap with a slit in it. It sometimes takes many skimming sessions to get rid of all the oils in a system. Some installers are sloppy with pipe dope and that can require more skimming.

Bob

Fred

If you are skimming it properly, from a skim port, above the water line, and very slowly, you should only have to skim it a few times , when it was new and after that it should only need skimming when some work/piping is done that might add oils back into the system.
Is the water level correct in the boiler?
Check the mains and radiator run-out, where you hear the hammer and make sure they are pitched the right direction and don't have any sags in the pipe. Anywhere water can pool, in the pipes is a place for potential hammer.
Was the boiler piped correctly?
Are all the radiators pitched correctly? Towards the supply pipe, if one pipe system, towards the drain side, if a two pipe system.
Make sure the pressure is low. Pressuretrol should be at .5 PSI Cut-in (scale on front of Pressuretrol and a Differential of "1" on the white wheel, inside the Pressuretrol.

JodiMe

Thanks, all. It’s being skimmed from a port above the water line. It was installed properly as per our own heating guys (found through this forum). Pipes are good, pressure is low; we’ve had success with skimming previously.

Our guys assumed that it hadn’t been skimmed when it was installed. That’s why we had a skim port installed, so we could do it on our own as needed. I’ve gotten about 4 gallons in just under 2 hours. Going to fill the rest of the bucket and call it a night.

Fred

That's a decent skim. Make sure the boiler isn't over filled. That can cause hammer also.

JodiMe

Oh, I know all about that, Fred! Before I came here, we had some other guys in who overfilled and then increased pressure (when all they came to look at was a leaking radiator). Not only did it cause horrendous hammer, I learned I did not like boiling hot rusty water spurting onto my floors.

It’s usually right at suggested level and I’ll be sure to return it there once I’m done skimming.