Boiler replacement without cleaning system

kmaguire64

My boiler is leaking from the top, as I refill it sometime multiple times a day, it looks like we are electing a new pope daily, and I can see the corrosion and wetness (before it heats up and dries) on the back right top corner. This system has not been flushed or cleaned in the 20 years since the boiler was installed. Wish I had found this forum when I moved in here and started to fix and mitigate the damage right away, but here we are dealing with this mess.

My question is, it being cold out should I just have the boiler replaced asap and then do a really good flush and cleaning of the system when it warms up, just suffer with refilling it constantly over the winter then replace and clean the system, or just have a really cold day at the house where the heat is off all day to replace and clean the system?

If the installing a new boiler into a dirty system as long as it is cleaned thoroughly at the end of the season isn't detrimental to the life of the new boiler I would lean towards that, as it would limit the time having to have the heat off I figure. Obviously don't want to do that if it is really bad for the new boiler though.

Jamie Hall

Adequate initial flushing of the system (I'm assuming we're talking about hot water here, not steam) shouldn't take much longer than actually removing and installing a new boiler -- so do them both at once. If, on the other hand, this is steam we're looking at, no initial flushing of anything is really needed -- though it wouldn't hurt to flush the wet returns, if any. But that can be done later, as needed, assuming the installer puts in suitable valves and Ts.

EdTheHeaterMan

In an older Hot Water system that has has lots of fresh water added oner the past couple of months (or years) you will have lots of rust build up that is getting mixed into the entire system, including the radiators. A quick flush when the system is being drained will get some of that crap out (CRAP is a technical term) but there will still be more that needs to be addressed. the addition of a strainer or a Dirt Mag® to keep as much of that crap from entering the new boiler will go a long way to keeping the system operational for years to come.

On the steam side, I agree with @Jamie Hall You can do it later but have the proper valves and tee fittings installed. I installed a steamer in a church and placed 2" pipe nipples on the bottom of the boiler with a 2" ball valve then another 2" nipple with a firehose connector on the outlet. I got an old 15 ft length of 2" firehose from a local fire company with the matching fitting. Each summer I could close the 6" king valve (already there from the previous boiler) & a valve on the return and build up about 10 PSI steam pressure and really blow out any rust or mud that was on the bottom of that boiler.

The neighborhood kids loved it when I made all that steam in the parking lot

Hap_Hazzard

It really depends on what type of system you have and how it's piped. If you have a one-pipe system with a steel pipe wet return, expect it to be pretty full of rust and sediment, so you'd want to flush that out or replace it, depending on how old it is and how easy it is to replace it. If you have a dry return, you only need to worry about the part that's under water, and only if it's piped with steel.

A few years ago, my wet return rotted out and I converted it to a dry return, and one thing I noticed was that, after the first few months, the boiler water stayed a lot cleaner than before. It turns out that most of the rust that happened initially was because the new pipe in the underwater part of the return rusted a lot initially, but once a layer of rust had formed, the rusting slowed down. Then one summer I decided to replace the underwater portion with copper pipe, as I noticed most of the pros here do. Now the water stays clear all winter. Just for kicks I decided to put a couple of sight glasses on the dry returns to watch the condensate flow, and that water is as clear as tap water. So the takeaway is that condensate doesn't normally have any rust in it until it sits stagnant in a steel pipe for a while, so the only part you have to worry about flushing is the steel pipe below the water line.