reading about various ways to get treatments into sealed CH systems.
Given that there is always a filling point (presumably 15mm thread) then how about a short tube with a one way valve at each end (same direction, obviously) full of treatment which you connect between the cold feed and the filling point?
Open the filling point, bleed a radiator (or open the relief valve which is less desirable) and your system is charged.
I presume, however, the Water Board may not be too happy about a connection between the mains and high concentrate treatment, although the filling loop achieves this anyway in normal use.
But AFAIK in normal use there is a check valve on the boiler side of the filling loop, and you'd be introducing nasties into the system on the mains side of the check valve. Bad.
(Of course in 'normal use' the filling loop has to be disconnected anyway, doesn't it? :-) !)
The application was for my workshop heating circuit, which is a secondary one run through a plate heat exchanger and zone valve from the main circuit.
In order to prevent the risk of freezing, if there is a failure, I used inhibitor with an antifreeze (Fernox Alphi-11). For the volume involved, this meant about £50 of the stuff, so I wanted to have a means of recovering it, storing and reloading it after work on the system.
The solution is a Hozelock compressed air plant sprayer together with an assortment of plumbing parts.
The sprayer has a lance of aluminium tube which when cut will conveniently fit an 8mm compression plumbing fitting. I went from that to a 15x8mm coupler and a washing machine tap.
The filling loop hose can be screwed onto the tap, and the sprayer is pumped up. The taps are simply opened and the liquid will be delivered into the system. I was able to get the system back up to
2 bar when cold by pumping reasonably hard.
The alternative approach is to use gel concentrate chemicals which come in a tube and are delivered by mastic gun, a short plastic tube and a nozzle that screws into a radiator.
However, following the instructions to inject against the pressure of the system is likely to result in a squirting of CH water up the wall. A better solution is to choose a radiator, close both valves and drain some water off. Pegler Terrier valves have an inboard drain c*ck which helps here, but otherwise undo a union remembering that sludgy CH water stains. Close the draincock/union and inject gel. Refit radiator vent plug and open radiator valves. Vent radiator and if needed add some water through the filling loop.
If you are doing a lot of underfloor heating then a good investment is a pressure test pump. You can also use it to pump cleansers and inhibitors into a system. Toolstation have one (62484) at £170, although I got mine a bit cheaper through Pulsar.
Ummm, i've always drained at drain point... don't isolate anything... which drains from the attics down. I then put treatment into the attic ones, and refill. Only mess is then in the cellar.
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