How best to swap PB plastic pipes around on a radiator

[iankenn]

Hi All,

I've moved into a relatively new house which has plastic pipes and push fixings for the central heating system. The problem I have is that 2 of the radiators have been plumbed in incorrectly and the water flow is going to the wrong valve.

I thought this would be easy to solve by simple swapping the plastic pipes around.... One minor flood in the kitchen later... Doh!

What I would like to know is the simplest way to change the pipes over with out another flood. Do I need to drain the system, closes all the rad valves?

The systems is a closed system with a pressure vessel fitted above the hot water tank.

Thanks in advance

 

[John506]

Buy 2 bi-directional TRVs and fit them, then it doesn't matter which side what pipe is connected to.

To change them either drain system or create a vacuum, there are loads of posts on here on how to go about doing both.

 

[John506]

Well thats what I would do anyway, but to answer your question.

drain system until pressure is dropped to 0bar. then (with a few people) undo the TRV & Lockshield nuts and place your thumb over the pipe, and get someone else to do it on the other side, then get another 2 people to plug each side of the rad with their thumbs, then quickly as you can connect the pipes up the other way round (thats if the TRV and lockshield nuts are the same and actually fit).

Alot of thumbs but that is the quickest way without having to drain the system fully if you don't want to go into vacuums because it's not as easy on a sealed system.

 

[iankenn]

Thanks for the responses John506. I'm going to investigate the vacuum option as I'm rather short of thumbs for the quick-fix method.

One other question about vacuums: If I'm going to be removing both pipes from the radiator (to swap them around) would this not break the vacuum?

 

[seco services]

is the rad already fitted with a trv and a locksheid valve ?

 

[JohnD]

why don't you just swap the valves and leave the pipes where they are?

You remind me of the two Australians who moved into houses next to each other, and found the builders had given them the wrong keys to their garage doors

So they swapped doors

 

[seco services]

why don't you just swap the valves and leave the pipes where they are?

You remind me of the two Australians who moved into houses next to each other, and found the builders had given them the wrong keys to their garage doors

So they swapped doors

does seem like a simple job made hard.

 

[D_Hailsham]

The problem I have is that 2 of the radiators have been plumbed in incorrectly and the water flow is going to the wrong valve.

OK, stop there for a moment and explain why you think the water flow is going to the wrong valve.

 

[iankenn]

2 of the rads in the house never get hot, the bottom corner by the TRV is always cold. I have tried to bleed these and no air is coming out. From cold the hot water for these 2 rads comes in through the pipe attached to the non-thermostatic valve (This is the actual valve with drain-off: http://www.pegler.co.uk/prod/taps_mixers.aspx?ID=40003)

All of the other radiators in the house, which do get hot have the hot water flowing in through the pipe connected to the TRV.

Should the flow of the hot water go to the thermostatic valve, through the rad and out via the other valve? If this is the case, swapping the valves to different ends of the radiator would not solve the problem, or would it?

 

[JohnD]

so the problem you have actually got is "some radiators do not get hot enough"

1) Verify the TRVs are fully open and not jammed (if you can see how to take the thermostatic heads off, see if the pin pops up and moves freely

2) try winding the lockshield valve in to Closed (count the turns so you can put it back to the same setting) then see how many turns it takes to fully open.

If it was very nearly closed it will have been obstructing flow.

When you have fully opened it, close some or all of your hotter radiators and see if this one gets hot.

If so, you need to balance your radiators.

Hopefully your system contains inhibitor and does not have black water and sediment in it which can cause blockages. What is the diameter of the pipes?

Useful background on http://www.diynot.com/forums/viewtopic.php?t=37170

 

[iankenn]

One other thing the pipes are bendy plastic pipes which come through a hole in the plaster-board wall behind the rad (which looks like it was created with a fist or hammer) and then the pipes sag down underneath the radiator to the valves.

 

[D_Hailsham]

All of the other radiators in the house, which do get hot have the hot water flowing in through the pipe connected to the TRV.

So you assumed, possibly wrongly, that the TRV was on the wrong end!

Should the flow of the hot water go to the thermostatic valve, through the rad and out via the other valve?

It does not matter which end the TRV goes, provided the water is flowing through it in the correct direction - hot pipe is in, cooler pipe is out. That all depends on the TRV! Some are one direction only (shown by a single arrow) others are bi-directional (two arrows at right angles.

If the TRVs are OK, then the problem is caused by the rads are not balanced.

 

[rssteve]

phone the plumber if the house is relatively new and they have not worked from the start.

 

[D_Hailsham]

If it was very nearly closed it will have been obstructing flow.

The design of the typical LS valve means that it is fully open when about one and a half turns opened from closed. If you look at the typical TRV valve, e.g.TRV4, you will see that the orifice through which the water has to flow is very small - considerably smaller than the diameter of 15mm pipe. The TRV is therefore acting as a flow restrictor. If the LS valve is to have any effect, it must provide a greater restriction than the TRV, i.e be closed even more. That is why balancing always starts with all LS valves closed and then one is opened a quarter turn and the temp drop checked.

See Balancing TRVs or if you want to read something really heavy on balancing large systems. e.g office blocks etc, look at the Guides produced by Tour & Andersson.

The TRV 4 includes an integral balancing system, which needs a special box spanner. That's the reason for the numbers on the black ring round the pin of a TRV4. The valve comes set to no 6 (fully open) the other numbers reduce the size of the opening in the side until, when on 1, it is about 1mm square.