How can I add inhibitor to my sealed central heating system? Can anybody point me in the right direction please
Inhibitor adding
- Thread starter hornet
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How do I get it into the system - do I connect up to a rad?ChrisR said:
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Hornet:
Despite the fact that it's quite unnecessary, I've been using a corrosion inhibitor in my heating water for about 15 years now.
The chemical most commonly used here is potassium nitrite.
Open your phone directory to "Water Treatment" or look on the internet for Industrial Water Treatment. Probably the biggest company in this business is Drew Chemical, so if there's a Drew Chemical office in your area, you can probably buy some potassium nitrite from them.
How to inject it into your heating system?
Both the cold water supply for your washing machine and your boiler drain valve will probably have a hose thread on them.
Wrap a garden hose around the inside diameter of a 5 gallon pail and reach into the bottom of the pail and pull out the bottom of the hose and stuff a funnel in that end. Now, pour your potassium nitrite into the funnel so that the hose actually fills from the bottom so you don't get any air bubbles in the hose. Now connect one end of that hose to the boiler drain valve and the other to the cold water supply pipe to your washing machine.
Open the boiler drain valve.
Open the washer cold water supply valve, and inject the corrosion inhibitor into your heating system with the water supply pressure.
Close the boiler drain valve. Close the cold water supply valve to the washer.
Allow the chemical to circulate in your system for a few days, and then check the concentration of corrosion inhibitor by testing it's pH. The concentration will be effective as long as the water is sufficiently alkaline.
But, the only time you really should use a corrosion inhibitor in your heating water is if you're draining the water often and replacing it with fresh water. Why do you feel you need to use a corrosion inhibitor in your water?
Also, it occurs to me that I can do it the way I described because my heating system is much bigger than you'd find in a typical house. In a house, injecting water using the cold water supply pressure is a bit risky because the volume of the system is so much smaller that you could over pressure it and pop the pressure relief valve on your boiler. In that case, you might be best off just draining your system down a bit, removing an air vent from the highest elevation radiator in your house, pouring some corrosion inhibitor in, adding water to the system and bleeding off the radiators until water starts to come out, then turning on the circulating pump to mix the chemical into your heating water.
Despite the fact that it's quite unnecessary, I've been using a corrosion inhibitor in my heating water for about 15 years now.
The chemical most commonly used here is potassium nitrite.
Open your phone directory to "Water Treatment" or look on the internet for Industrial Water Treatment. Probably the biggest company in this business is Drew Chemical, so if there's a Drew Chemical office in your area, you can probably buy some potassium nitrite from them.
How to inject it into your heating system?
Both the cold water supply for your washing machine and your boiler drain valve will probably have a hose thread on them.
Wrap a garden hose around the inside diameter of a 5 gallon pail and reach into the bottom of the pail and pull out the bottom of the hose and stuff a funnel in that end. Now, pour your potassium nitrite into the funnel so that the hose actually fills from the bottom so you don't get any air bubbles in the hose. Now connect one end of that hose to the boiler drain valve and the other to the cold water supply pipe to your washing machine.
Open the boiler drain valve.
Open the washer cold water supply valve, and inject the corrosion inhibitor into your heating system with the water supply pressure.
Close the boiler drain valve. Close the cold water supply valve to the washer.
Allow the chemical to circulate in your system for a few days, and then check the concentration of corrosion inhibitor by testing it's pH. The concentration will be effective as long as the water is sufficiently alkaline.
But, the only time you really should use a corrosion inhibitor in your heating water is if you're draining the water often and replacing it with fresh water. Why do you feel you need to use a corrosion inhibitor in your water?
Also, it occurs to me that I can do it the way I described because my heating system is much bigger than you'd find in a typical house. In a house, injecting water using the cold water supply pressure is a bit risky because the volume of the system is so much smaller that you could over pressure it and pop the pressure relief valve on your boiler. In that case, you might be best off just draining your system down a bit, removing an air vent from the highest elevation radiator in your house, pouring some corrosion inhibitor in, adding water to the system and bleeding off the radiators until water starts to come out, then turning on the circulating pump to mix the chemical into your heating water.
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hornet said:
Hi "hornet"
I added inhibitor in my system by draining my by bathroom radiator approximately 2 litre. Then remove a 1/2 inch plug on side of radiator using a an angled funnel added the inhibitor. It was slow and messy but it worked.
Fit the 1/2 plug. I checked the pressure on the boiler. It had dropped a little. I brought the pressure to 1.5 mgbar by filling loop. Fired the boiler and bled the system. Job done in 45 minutes. Hope this helps.
Nestor_Kelebay said:
UK heating systems usually contain cast iron in the boiler, copper in the pipes, brass in the valves, pressed steel in the radiators, and sometimes stainless steel or aluminium parts. They also usually contain traces of acidic flux, and steel and copper swarf. So they get electrolytic corrosion despite being almost closed systems, as well as the initial rust as disssolved air from the first fill attacks the radiators. We have several proprietary brands of corrosion inhibitor.
The water companies wouldn`t take kindly to chemicals and "wholesome" water (from a mains fed washing machine .as is common in UK) coming in contact..at the very least a double check valve is required on the hose..and the concentrates sold in the UK are supplied with nozzles to inject through Rad. air vents. ..........So advice back across the pond.......Empeach Bush 
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JohnD:
North American hot water heating systems also generally have a cast iron boilers, copper piping, brass valves and some stainless steel or aluminum parts.
But, over here the feeling is that in a closed hot water heating system, the amount of corrosion that occurs each time the heating system is drained and refilled with new water is small, and that that new water quickly becomes oxygen depleted and ionically dead, so won't support galvanic corrosion between the different metals in the system. Certainly we recognize that it's not a good idea to replace the water in the heating system any more often than necessary, but adding corrosion inhibitor to that new water is not at all common over here. I'm one of the rare exceptions.
I use corrosion inhibitor in my heating water because I've never been comfortable with the fact that the water in my heating system becomes black with iron oxide, and the only place that iron can come from is from corrosion in my boiler.
What I've been telling DIY'ers over here on the internet is that when they want to drain down their heating systems for repairs, to save the old water in 5 gallon pails and siphon it back into a top floor radiator through an air vent after the repair is done. That prevents them from introducing any more oxygen or hardness into their heating systems, and also gives them a fool-proof way of refilling their system with the correct amount of water.
North American hot water heating systems also generally have a cast iron boilers, copper piping, brass valves and some stainless steel or aluminum parts.
But, over here the feeling is that in a closed hot water heating system, the amount of corrosion that occurs each time the heating system is drained and refilled with new water is small, and that that new water quickly becomes oxygen depleted and ionically dead, so won't support galvanic corrosion between the different metals in the system. Certainly we recognize that it's not a good idea to replace the water in the heating system any more often than necessary, but adding corrosion inhibitor to that new water is not at all common over here. I'm one of the rare exceptions.
I use corrosion inhibitor in my heating water because I've never been comfortable with the fact that the water in my heating system becomes black with iron oxide, and the only place that iron can come from is from corrosion in my boiler.
What I've been telling DIY'ers over here on the internet is that when they want to drain down their heating systems for repairs, to save the old water in 5 gallon pails and siphon it back into a top floor radiator through an air vent after the repair is done. That prevents them from introducing any more oxygen or hardness into their heating systems, and also gives them a fool-proof way of refilling their system with the correct amount of water.
Sounds like too much hard work to me!! Surely as soon at the water comes into contacy with air it is re-oxygenated thus no better than putting fresh water back into the system?
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Well, it would take someone who knows more about it than me to decide that for sure. My feeling is that you'd be putting in less oxygen (and no additional hardness) by putting the old water back in.
Not a bad idea, you can save the water with its inhibitor for re-use if, like me, you're a bit mean. I'm very pleased to say that I now get no sediment or grit out of my syst (did before I cleaned it, though).
I have been toying with the idea of filling my syst with deionised water, should have no hardness salts or other undesirables in it (though I bet it would soon pick some up in the old system). Can't see where to buy it by the 100 lites, though.
I have been toying with the idea of filling my syst with deionised water, should have no hardness salts or other undesirables in it (though I bet it would soon pick some up in the old system). Can't see where to buy it by the 100 lites, though.
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