I have some used schedule 40, 3” steel well pipes that are 31’ long that i want to remove the rust on the inside of pipe. It would be nice to remove outside of pipe as well to stop rusting but proably isn’t necessary. Here is what i am using for. I have a hot water boiler and i am going to run 10- 31’ long sections of steel pipe welded together to get hot water in my building. We do run chemical in boiler to prevent rusting and my thoughts is this will clean out the pipes and i will get extra contamination in boiler?. The pipes will be buried underground and then spray foamed with closed cell foam and then buried in sand. I was not planning on protecting foam as i was told it will not soak in water?

The reason to remove rust on inside is to keep from debris rust and other contaminants into our boiler. The outside is proably not an issue because once its spray foamed it should be sealed and probably not rust and cause further decay. So if only cleaning iside i was thinking of buying rubber hose pipe seals and putting on each end and filling with vingear. Probably cost me 500 in vinegar. Or incase pipe all around in pvc and cap both ends fill with vinegar. And clean both in and out. I feel i should try to clean the inside but also feel all this is over kill and should just hook up to boiler and try to drain contamination at the boiler blow down pipe periodically. I will need pipes in a couple weeks so will probably need them do all at once or half at once so wont be able to reuse vingar.

1. Will thr spray foam pick uo water and loose r value?

2. Do i try to clean inside of pipe and outside or just inside or dont bother any?

3. Is there a better chemical than vinegar and if so what and what dilution, with out breaking pocket book.

4. If vinegar is the correct material what dilution and how long should it be soaked.

The outside would be easy with a little sand blasting, you may need to clean the outside to get the foam to stick, inside if you can find a brush like a flu brush for your boiler for a 3 inch pipe it would allow you to give a scrubbing action to the inside of the pipe.

I'd think a brush like Bob said with some type of navel jelly or other rust remover on it and use little PVC pipe to make it long enough to reach. Then flush with a lot of water. A fire hose would be great if you have a connection to a fireman.

Common length for pipe is 21' are you sure it's 31'?

Yes 31’ sections

If your that worried, can you put a filter in
Or use stainless

3 inch is big, maybe too big, I ran 1-inch plastic, for a 50 by 65-foot building and had in floor heat,

Or: Copper/PVC.

Thanks for some suggestions, some feedback

I realize I could use new copper or stainless but it’s cost prohibitive, it very expensive at 3” with pipe and fittings. So hence the question on how do I clean the inside effective.

Trapper dahlgen. This is for a big industrial building that is 65,000 sq ft and planning for room for future expansion. So I can’t run it with 1”

Boiler tubes are sometimes cleaned with very high pressure water jetting. Like 10,000 plus psi.