Maintaining a low-pressure boiler can help to cut the costs of a professional boiler engineer, and one good way of helping to keep your boiler in excellent condition is to use chemicals to treat the water so that there is less risk of it developing corrosion. Putting chemicals into the boiler can also assist in preventing the build-up of dangerous bacteria and mold, which can lead to serious illness such as legionaries disease. Performing the water treatment yourself can take a bit of time, but if you are careful, you can save money and help your boiler to last for longer.
Step 1 - Removing the Old Water
Make sure that your boiler is turned off at the mains in both electricity and water, and then use the blowdown nozzle to release the water, sludge and solids out of the tank. Place a bucket on the ground to catch the water, and wait until it is completely empty. Take this water and dispose of it in a drain or into a sewage outlet, don't pour it down the sink. Check the boiler for signs of corrosion, and then allow the water to fill up the tank again. Put steam into the feedwater tank, and heat to 180 degrees, as this will cause any excess oxygen to be vented off. This will help prevent corrosion.
Step 2 - Apply the Water Treatment
Water treatment for a low-pressure boiler is essential, particularly if you have a steel lining in your boiler. If your boiler is cast-iron, you should use the purest water possible, and you may find yourself limited in what chemicals you can use. If you have hard water, then the likelihood is that you will have lot of mineral contaminants, and may end up with scaling on the inside of the metal, while soft water is more likely to cause corrosion. Low pressure boilers will also require a great deal of oxygen scavengers in the chemical compounds.
Step 3 - Using the Correct Dosages
Knowing how much of each compound you need to put into the water is essential. Sodium Sulfite, for example, which is a common oxygen scavenger, needs to be 10 parts for every 1 part of dissolved oxygen. Feedwater can contain 4 parts per million, and so you should place 40 parts per million of Sodium Sulfite. If you are using a mixed chemical treatment, containing oxygen scavengers, biocides and phosphates, you will probably be able to find instructions for use on the side of the bottle.
Step 4 - Using the Chemicals
Insert the chemicals into the tank, and then leave the boiler to heat as usual. Once the hot water has reached the required temperature, draw off a little bit of the water using the blowdown, and then add a little more of your chemicals to the mix. You should use the blowdown regularly to remove sediment and chemical by-products from the water. This will also allow you to check on the progress of the chemicals. Have your water tested occasionally by a local water company, and check your boiler regularly for signs of corrosion or pitting.