30 Nov 2022
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United Kingdom
Hi all,

hoping for some help/guidance on this one. I've got a UFH system downstairs that had to have the blending valve replaced. It was a fairly bad leak so Im assuming the system will need topping up/bleeding but the plumber that replaced the valve didn't do it.

Obviously google search results show the process is fairly easy (he says) but I seem to have fallen at the first hurdle. looking at the filling loops there is no way to "open them". So my question is what is this valve on the end? Is it one-way??? If I removed the hose connector and loosen water starts to come out, but that would mean I have to replace the valves with an isolvation and completely refill the system (possibly beyond what I want to do).

The main reason for doing this is I think there is air in the system. I have bled/refilled the upstairs rads, but I think something is sticking in the UFH as if you look in the 1st picture the flow valves show flow on 2 areas but not on 2 others (and this is when the system is off).

I hope a good mains refill will clear any debris out as the flow meters dont appear to be able to be set/adjusted (this is controlled by the actuator up top).

As always any help or advice is appreciated.



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The loops won't have lost much water, if you think about it, most of the water is held in the loops in the floor which is below the level of the manifold/blending valve.

That being said, the answer to your question is the filling spigot fitting will twist open using the top knurled ring. The pipe goes on the spigot then you twist the valve open. It would then be bled using the manual bleed valve on the top.

The flow meters are another issue and may just be stuck, try tapping them. The alternative would be to isolate the manifold and pop the meters off and check they are moving freely.
Thanks for the advice Rob,

My main worry is that there is air in the system as I seem to have cold spots and I was assuming (rightly or wrongly) that this could have been introduced when the blending valve was changed.

I did try undoing the knurled ring on the top and water started coming out the top of it so I stopped, but maybe it was just me being over cautious. Im hopful that re-pressuring the system will force any air out and potential debris on the flow meters.

I've seen the videos on how to fillthe system but it has the flow meters on the top rail and the actuators on the bottom. Do I still need to fill vai the top or do I fill via the flow meters?

I did try undoing the knurled ring on the top and water started coming out the top of it so I stopped
Not the hex nut at the top of that brass fitting that contains the white bleed valve. The bottom part of the brass fitting where the open ended pipe (spigot) points downwards. I am presuming that the bottom knurled ring just grips the spigot on the fitting (like an outside tap fitting) and the higher one locks the valve shut. The minute you release those valves then the pressure in the UFH will want to push the water out. You need to isolate the main system manifold valves (red and blue) that should be at the bottom of the manifold, then release the pressure out of the UFH. Then attach a hose to the top and bottom and feed tap water in from top with the bottom hose into a bucket, if there is any air in the loops then that will be pushed out the bottom hose. Submerge the outlet pipe under some water in the bucket so you can see any air bubble being forced out.

Shouldn't matter that the flow meters are on the bottom as long as there is a path for the air to escape and then bled properly.

Don't forget, depending on how much water you replace, you may need to add more inhibitor.
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perfect! thanks for the advice I really appreciate it!

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