Cleaning Heat Exchanger Tubes

With more and more people having heat exchanger systems to heat the water in garden swimming pools, cleaning heat exchanger tubes is another maintenance routine that a DIY enthusiast can do for themselves. Apart from the obvious advantage of protecting against an unexpected and sudden failure in the heat exchanger system, regular and effective cleaning of the heat exchanger tubes will prolong the life of the whole unit and make sure it’s working to its maximum efficiency. You should consider at least inspecting heat exchanger tubes every three months and, to really protect the whole unit, be prepared to have a regime for cleaning heat exchanger tubes at least every six months.

Methods for Cleaning

Having disconnected and removed the heat exchanger tubes form the system itself; the first thing to do is remove any loose material near the ends of the tube. This is a sensible precaution as you don’t want to unnecessarily push anything into the tube when you do start cleaning inside it.

Brushing

The next operation in cleaning heat exchanger tubes is to remove any loose material that is inside the tube. This can be done with a variety of techniques dependant to some extent on the length of the tube. It’s advisable to try and keep the tube dry initially if at all possible. ie. Not rushing to forcing a water-jet down it straight away.

To begin the tube cleaning process; push an appropriately sized brush down the tube, the brush needs to have some strong nylon bristles. Whilst any loose material in the tubes should really have found its way to the filters whilst the unit was in operation, if there is any loose material in the tubes a good brushing up and down will remove it.

Scraping

Next, if you can see or suspect that there is something adhering to the wall of the tube you could try scraping the inside of the tube. When choosing what to use as the scraper you need to take into account the material that the heat exchanger tubes are made of. To avoid damaging the tube you mustn’t use a material as a scraper that is harder/tougher than the material the heat exchanger tube itself is made of.

Whilst actually puncturing a heat exchanger tube wall might be a remote possibility, scratching it could be a very real risk. You need to avoid scratching the inside of the heat exchanger tube as a scratch or imperfection inside the tube wall will provide an ideal surface for impurities to ‘cling’ to when you start up the heat exchanger unit after cleaning it. A strong plastic scraping tool is usually ideal for the job. Another method of scraping the inside of a heat exchanger tube is to run specially designed abrasive balls up and down the tube.

Water-jet Cleaning

Forcing water under pressure through heat exchanger tubes is a good idea to finish cleaning heat exchanger tubes. It will force out even the smallest particle of dirt that is loose - but was missed and not removed by a scraper. Water-jet cleaning may remove calcium deposits, but you’re more likely to need a chemical solution to solve that problem.

Chemical Cleaning

If the heat exchanger tubes have become contaminated with oil, or an oily substance, cleaning them with a mild detergent will usually be sufficient to remove it. If not and you need to purchase an industrial strength cleaner, make sure any chemical cleaner is compatible with the material the tubes are made of. If you have ‘hard water’ then you may well get Calcium deposits in the tubes.

Generally speaking an acid is applied to remove the deposits - so caution needs to be exercised in their use. Having said that, if the build up of any calcium deposits is minor - ‘washing’ the tubes in white vinegar can be all that’s required to dislodge the deposits. After cleaning heat exchanger tubes with chemicals - ensure they’re thoroughly rinsed with clean water.