Pressure Testing a Sealed System

[John2016]

Happy New Year People, hope you can still say that on the 12th.

I have a microbore 10mm central heating system which is about six years old. The system is a closed system with a pressured red tank, I have three two ports values.

I recently had a new central heater installed at a new location and the pipes were T'd off to install the new central heater.

For completeness, I would like to pressure test the system. My system operates at 1.5 Bar which is read on the red pressure tank.

I believe below are the correct steps, am missing anything?

• Start with system stone cold
• Disconnect filler loop, mains end
• Connect pressure test tank filled with water to filler loop
• Manually open zone valves
• Pump pressure pump to 2Bar
• Leave pressure for 30min and determine if it drops

Thank you.

 

[ianmcd]

you will need to leave it a lot longer than 30 mins, why do you want to pressure test it ?

 

[John2016]

Thanks Ian, how long would you recommend?

I would like to ensure I don't have any leaks.

 

[sxturbo]

when we pressure test cylinder blocks and heads, water pumps etc, we leave them for an hour, if no pressure drop and no sign slight wetness its good to go.

 

[oldbuffer]

1. In principle, what you are doing is right.
2. The norm is to pressure test at 1.5 times the normal working pressure.
3. You appear to have a sealed system. This will have a pressure relief valve which will open at 3 bar.
4. So in theory you should test a 3.0 x 1.5 = 4.5 bar to simulate the system running in fault conditions.
5. 4.5 bar is, in my opinion, a bit too close to maximum operating pressure for some items, so I would test at 3.5 bar.
6. Make sure there is nothing attached to the system (particularly expensive items like boilers (not central heaters)) which can be damaged by the test pressure.
7. The time the system should be pressurised depends on the type of piping:
7a. For all copper pipework, pump to test pressure and leave for a minimum of 30 minutes.
7b. For all plastic pipework, pump to test pressure, and over 30 minutes pump further to maintain that pressure, reduce the test pressure by a third and there should be no pressure drop over 90 minutes.
7c. For a mixture of copper and plastic, I'd test as if all plastic.

 

[John2016]

Thank you.

You have me thinking now, as I will have the boiler connected, tank and two port values connected...

I feel that due to the system being sealed and my mains pressure never goes above 1.5 bar, if I tested it to 2 or 2.25 bar, this would suffice.

What are your thoughts?

 

[oldbuffer]

1. Do it to 2 bar. Its a good deal better than no test, and, the pressure is only likely to go over that in a fault condition.
2. Even though your mains pressure never goes over 1.6 bar, the system pressure can be higher than that if the expansion vessel fails.

 

[John2016]

I had a thought which came to me.

Rather than spending money on a pressure test pump, would I just not pump up the expansion vessel, until it reached 2 bar (currently 1.5 bar) and then left it there to see if the pressure dropped while checking for any leaks?

Once the test was complete, I was release the pressure from the top to its standard.

 

[sxturbo]

I had a thought which came to me.

Rather than spending money on a pressure test pump, would I just not pump up the expansion vessel, until it reached 2 bar (currently 1.5 bar) and then left it there to see if the pressure dropped while checking for any leaks?

Once the test was complete, I was release the pressure from the top to its standard.

or you could just fill the system to 1.5 bar and leave it and watch for leaks. you'll soon know

 

[ianmcd]

currently 1.5 bar)

it shouldnt be

 

[John2016]

it shouldnt be

Oh I see.

What should it be? As I cannot get it over 1.5 bar.

 

[ianmcd]

Oh I see.

What should it be? As I cannot get it over 1.5 bar.

Expansion vessel charge pressure will be stamped on the vessel. usually 0.8Bar, which boiler do you have

 

[Madrab]

+1 ..... if not on the side of the vessel then it'll be in the boiler MI's