Reversed flow and return to radiator

[Lieutenant Scott]

Someone was telling me that it's important to connect the flow and return to the right ends of a radiator. But I cannot see a problem in water running the wrong way.

"The wrong way" would mean water flowing into the radiator through the balance valve and out through the thermostatic valve, but the radiator is symmetrical, and the valves are not one way (are they?), so what would be the problem?

The reason this came up is I'm plumbing in a new radiator and I've not marked which pipe is which that I've threaded out of sight under the floor. Although I can actually tell which is which as it's HEP pipe with metre markings on it, I wondered if I really have to know?

[John Rumm]

Some TRVs are one way. Some are described as two but work better on the flow side, and some are fine either way.

Make sure the TRV is a two way one, and it should be ok.

(Some of them begin to whistle a bit as they throttle the flow when on the return side).

[Brian Gaff]

Yes a place I use regularly has a radiator like that but its a rushing noise not a whistle. we call it Hissing Sid. I know its childish... Brian

[Scion]

John Rumm spake thus:

Some are either way, but need to be adjusted for the correct direction - this can be done after installation.

[Lieutenant Scott]

I've seen some which can be positioned with the knob vertically or horizontally, I assume these take it either way.

(There's going to be a few naughty replies to the above line.....)

I think I'll just connect the pipes correctly, in case of whistling (which would annoy the occupants (African Greys)) or future replacement of the valve by someone (or me being forgetful) who doesn't know the pipes are backwards. I've been told by a plumber he's had to correct a flow/return mix-up which caused a radiator to only get luke warm.

The HEP pipe metre markings will tell me which is which, as I bought a 50 metre length of pipe and used the two ends of the length to enter the house, with the middle being in the garage. Therefore the metre markings increase in one direction on one pipe and decrease on the other.

[Lieutenant Scott]

Is there a way to stop a radiator going bang bang bang (well quieter than a bang) when it heats up? Only one of them does it and it's the same model of radiator, and has the same model of valves, as the rest. The only difference is it's always the one that needs bleeding - the rest never do. It still makes the noise immediately after bleeding.

[Davey]

The online spec. for my valves says they can be used either way. In industrial pipework, the throttling valve is always put on the leaving side.

[R D S]

There's 2 the wrong way around in our house.

One lets out a "thunk" when it opens or shuts (or both) and and the other, in the bedroom, makes a whooshing noise.

If I could be asrsed i'd swap them round.

[Brian Gaff]

Well could be the mountings slipping as it expands I suppose. Brian

[Lobster]

Probably due to movement against its mounts as it heats up and expands. The mounts should normally have little u-shaped bits of plastic fitted to support the radiator, to prevent metal-metal contact and enable the rad to slide freely and noiselessly as it expands.

David

[John Rumm]

Sounds like it...

In similar circumstances (long run of pipes under a floor) I ended up getting a rad flowing the wrong way once. I was not particularly bother about the direction since I was using reversible valves. However I found that one became noisy as the valve did its thing, so ended up swapping it round in the end since it was in a bedroom.

That would suggest a non reversible valve used backwards.

[Lieutenant Scott]

The new radiator which came with brackets had no such plastic, and I don't think any of the existing ones do either. I think I'll just put up with it instead of trying to lift it off to insert the plastics and damaging the 8mm pipes. It only makes about 10-15 clonks about 1 a second.

[Dave Liquorice]

Can't say I've ever seen any plastci bits on the brackets or hoops on the back of radiators either.

Try giving it a woggle so where it bears on the brackets is changed. Or if you can get at the bearing points with a long thin stick put a tiny drop of engine oil on them.

[Lieutenant Scott]

I have er... woggled it (I think you meant wiggled, I don't have a boy scout to hand) - if that doesn't work I think I can get oil onto them, the brackets are only about 5 inches from the edges as it's a small radiator.

[Alan Braggins]

Mine came with little plastic clip on bits for the bracket.

[Lieutenant Scott]

I'm not convinced those would last long with the weight of the radiator and the sharpness of the metal brackets.

[Andrew Gabriel]

the sharpness of the metal brackets.

Sometimes the radiator does cut through them - has happened to one of mine, but the other 8 or so have lasted 10 years so far (or at least, don't make expansion/contraction noises), and 4 of them are heavy triple panel radiators. (The ones that's failed is a double.)

[Andrew Gabriel]

the right ends of a radiator. But I cannot see a problem in water running the wrong way.

valve and out through the thermostatic valve, but the radiator is symmetrical, and the valves are not one way (are they?), so what would be the problem?

which pipe is which that I've threaded out of sight under the floor. Although I can actually tell which is which as it's HEP pipe with metre markings on it, I wondered if I really have to know?

The other important thing is that the return must be from the bottom of the radiator. Flow can be into bottom or top.