Replace Drayton TRV3 with Danfoss TRV?

[Aldrich]

Hi

I need to replace two Drayton TRV3 thermostatic valves as they are now very old. Drayton told me that the TRV4 will be a direct replacement, but I am also considering the new Danfoss RAS-C2 TRV because it looks good quality and is much cheaper than the TRV4.

I have no experience of plumbing. Would you expect the Danfoss to be a direct replacement for the Drayton, or would I need to modify pipe lengths etc?

When I fit the new TRV, should I replace the olive?

Do I need to put any sealing substance around the olive?

Finally, after fitting the valves I shall need to add new inhibitor to the system, which is sealed. I intend to use Fernox MB-1. Any suggestions of how to add it to the system please?

Thanks

David

[Andy Hall]

Danfoss make good quality products. I would personally use the TRV4 because I have had good results with them for 30 years, but Danfoss is also a good brand.

You would need to check dimensions from manufacturer datasheets but they should be the same or close enough to be within pipe movement without cutting.

It is best to do so because you will replace the nut as well. The main challenge will be removing the olives without damaging the pipe. A small hacksaw can be used for this, or a Dremel tool with cutting wheel. Cut almost through the olive and then ping off with a screwdriver. There are also special olive removal tools from plumbers merchants.

For the purpose of sealing, no. I sometimes smear some PTFE paste sealer around olives, but really by way of a lubricant rather than needing to seal. If a pipe and fitting are OK and undamaged, then they should seal by tightening only.

A couple of options:

- At a high point in the system, put in a tee with vertical pipe from the branch and a lever ball valve. You can put a funnel into this for adding the liquid MB-1. Take off the handle afterwards so that the valve is not inadvertently opened.

- Use the gel version of the inhibitor. This is a little more expensive but can be squirted in with a mastic gun. However, it's easier to do it when the system is empty rather than doing as the manufacturer suggests and injecting against the pressure.

[Doctor Drivel]

Danfoss invented the TRV.