how to powerflush sealed central heating system.

[Bouba]

I have a vaillant boiler with 10 radiators.I have drained and refilled all radiators, but still they are warm on top and cold at bottom.I also have to remove air from an upstairs towel rail every other day,however it does get hot.

Would like to hire a power flush machine.Could someone point to me how to powerflush the system as been quoted £300 to do this.Strapped for cash so would like to give this a go.

 

[Mottie]

I would imagine you would get instructions with the machine you hire but from memory, some chemical stuff was put in a week or so before flushing then when the bloke came to powerflush, he disconnected one rad downstairs, connected the machine to the flow and return, shut off all rads bar one, power flushed it, shut it off, opened another, power flushed that and so on.

If you are strapped for cash, why don’t you remove each rad one at a time and physically flush it out in your back garden with a hose, giving it a good shake up between flushes until it is running clear, do this to all the other rads, put some chemical flush in and run the system for a few days, drain and flush with clear water a couple of times then refill the system, adding inhibitor.

 

[oldbuffer]

1. Look up the Kamco web site and read their instructions on how to do it.
2. The last time I hired a power flushing machine before buying my own it cost £70 for the day, plus about £50 for chemicals (big system).
3. Whatever you do make sure the machine is either outside (with precautions against rain) or in the bath. Maybe its just me but its just to easy to forget which valve to operate and flood wherever the machine is. If in the bat make sure you clean it regularly as you go, the muck that comes out leaves very difficult stains if you don't.
4. It must be one of the most boring jobs on earth. Once you've connected it all up, its sit down doing valve change overs for at least 1/2 an hour per radiator. The only excitement is going from one radiator to the next, turning the first off and the next on.
5. Depending on the chemical you use, the residue will have to be neutralised at the end of the job.
6. You should really check the total dissolved solids and pH of the system water before and after the flush.
7. The advantage of a power flush over removing each radiator and flushing it is that the power flush also cleans the pipework. However, no powerflush will clear a totally blocked pipe or radiator. There must be some flow to allow the chemicals to work.

 

[ianmcd]

If it is costing £300, and it is done correctly that is a good price, however sadly a lot of cowboys do power flushing and haven't a clue what they are doing

 

[Gasguru]

When you say the radiators are warm at the top and cold at the bottom what's the temperature drop between the pipes each end?
If it's less than say 20 degrees then you do indeed have a problem with sludge in the radiators but I'd be very surprised if that's the case.
Most warm radiator problems are down to balancing, failing diverters, bypass valves etc.

Powerflushing is very rarely carried out by those in the trade let alone a 1st time diyer.
The first job of powerflushing is removing and replacing all the TRVs with lockshields to get the flowrate up but few will say that.

What Vaillant model?

I'd guess you've probably got a leak on the system hence the air in the top rail.

 

[Bouba]

it is a Vaillant Turbomax boiler.The radiators with cold spots have Trv's fitted to them.
When the boiler is on on full mode at 82 degrees then all the radiators get warm,however the ones with the trv's only get warm when on full no 6.If i reduced it to 3 or 2 it does not even heat up.The other radiators are also not too hot to touch but warm on top and cold at bottom.Hot water works absolutely fine.

 

[Gasguru]

When you say the radiators are warm at the top and cold at the bottom what's the temperature drop between the pipes each end?
If it's less than say 20 degrees then you do indeed have a problem with sludge in the radiators but I'd be very surprised if that's the case.
Most warm radiator problems are down to balancing, failing diverters, bypass valves etc.

Open the TRVs to their maxiumum setting and then feel the pipes as I've said before...

I don't think you understand how a TRV works...when the TRV senses the air temperature in the room matches the set temperature on the TRV head the flow is reduced and shut off..the radiator cools.

 

[ianmcd]

you dont need a powerflush