Plumbing question

[Pford75]

Not strictly PP, but need the sage advice of the forum.

We have a dual stream pressurized water system. This supplies both our central heating and taps/showers etc. A new plumber came to service the boiler etc. Yesterday (the previous one has moved). He did the usual sucking of gums etc. And moaned about the previous guys work. However, one thing he said was worrying - he claimed the installation was dangerous due to potential water contamination.

I usually take a lot of tradesmen moans with a pinch of salt (they seem to want to create work for themselves)....but I don't know how to respond to this. Bear in mind that I am not a plumber and know very little about it (in comparison to other building work).

Basically, the alleged problem is.....we have a central heating circuit divided into 6 zones...this works fine. But we also have 2 heated towel rails which we wanted to run during the Summer when the heating is off. Therefore, the installer supplied 2 suitable for this purpose (ie. They are copper lined I believe to prevent corrosion). They are installed on the hot water supply, with a bronze pump on a timer switch to remove any dead legs. The new plumber says this will contaminate our water supply, since this is supposed to be potable.

I was under the impression that this is a fairly common installation (water circuit towel warmers are common and distinctly different to those for CH). We have had the installation for 5 hrs now with no noticeable problems and other plumbers/builders have fitted bathrooms etc and not commented.

Any advice or thoughts on how to handle?

 

[Flyfisher]

I can offer some thoughts, but I wouldn't call it advice as I'm still learning about this sort of thing myself.

My understanding is that towel rails are usually fitted in the circuit between the boiler and the HW tank and the CH is tapped off from this circuit via the CH pump.

So, boiler on, and it heats the water, which rises though the towel rail and then into the HW tank coil to heat the tank of DHW (or perhaps it's in the return from the DHW tank, but the same thing will happen). The DHW tank is fed from the mains supply, so is potable, and never comes into contact with the boiler circuit water (which will normally contain anti-corrosion additives anyway, so definitely not potable!). Any hot water in the house from taps and showers should therefore be potable.

When the CH is turned on, the pump pushes the boiler hot water through the radiators. There may be some heat leakage past the pump when the CH is off, but it should be minimal.

Thus the towel rail should heat up whenever the boiler is operating, regardless of whether the CH is on or off.

If the towel rail is connected into the DHW circuit, i.e. the hot water that comes out of the tap, then presumably it will only become warm when a tap (or shower?) is running? I don't recall this ever being the case in any of the houses I've lived in.

If only plumbers would provide an 'installation diagram' for the works they do!

Coincidentally, I gave some thought to all this when planning the new bathroom I'm currently working on but eventually gave up because the pipework would have been quite fiddly. So, as it's only a downstairs loo with a shower, I decided to use an electric towel rail instead.

 

[Onetap]

They are installed on the hot water supply, with a bronze pump on a timer switch to remove any dead legs. The new plumber says this will contaminate our water supply, since this is supposed to be potable.

I was under the impression that this is a fairly common installation (water circuit towel warmers are common and distinctly different to those for CH). We have had the installation for 5 hrs now with no noticeable problems and other plumbers/builders have fitted bathrooms etc and not commented.

It has lasted for all of 5 hours? That is impressive.

He, and you, are both correct. These are 'not to current standards' but were and are still, a common installation. The problem is that legionella and other organisms will proliferate in tepid water and there is a theoretical and incalculable risk. There are puindits who will tell you that legionella has never affected a domestic property and it is not a risk; untrue. Legionella will colonize any warm water (blood heat is ideal for them, room temperature is tolerable). No-one has ever been prosecuted in respect of a house in the UK because the legislation is all based on the Health and Safety at Work Acts.

When I worked for the NHS 25 odd years ago, they were busy ripping out towel warmers that were connected to the domestic hot water system; legionella had just been discovered. However their residents were 'at risk'.

The current water regulations require all the domestic hot water pipework to be insulated. These towel rails were discussed on a plumbing forum recently and there were many plumbers who were still fitting them. You can buy chrome-plated copper towel rails for this application. A plated steel towel rail should only be connected to the central heating system.

 

[Lime]

It is important to make a clear distinction between:

1. ~a towel rail supplied from the boiler pipework feeding the heating coil within a hot water cylinder.

2. ~a towel rail supplied from the hot water cylinder using hot water normally fed to taps.

a bronze pump on a timer switch to remove any dead legs. The new plumber says this will contaminate our water supply, since this is supposed to be potable.

I presume the plumber is referring to water contamination from the pump mechanism and not any bacteriological source or growth.

I would never describe a domestic hot water supply as "potable".

 

[Onetap]

2. ~a towel rail supplied from the hot water cylinder using hot water normally fed to taps.

a bronze pump on a timer switch to remove any dead legs. The new plumber says this will contaminate our water supply, since this is supposed to be potable.

I would never describe a domestic hot water supply as "potable".

A bronze pump is normal on a domestic (tap) hot water circulating system. A standard ferrous CH pump would rapidly fail due to the oxygen in the hot wtare and the lack of corrosion inhibitors. I'd think the system is as 2 above.

A domestic hot supply is supposed to be of potable quality, hence the byelaw 30 compliant water storage cisterns, lead-free solder, etc.. Having said that, many old water storage cisterns were/are ghastly cess pits and it is not safe to assume that domestic hot water is safe to drink.

 

[Pford75]

Thanks for the feedback......bottom line, should I change it?

 

[Lime]

Thanks for the feedback......bottom line, should I change it?

Assuming your system is type "2" from my previous post.
If your concern is bacterial growth the answer to your question depends on the maximum temperature of the hot water.

 

[Onetap]

Thanks for the feedback......bottom line, should I change it?

Personally I would, eventually, when I got around to it etc., but I wouldn't worry about it.

If the hot water system doesn't stay tepid for long periods and if the cold water tank isn't a fermentation vat for assorted decaying flora and fauna, the risk is reduced. If there is anyone with a compromised immune system using the house or very young or very old, the risk is greatly increased. You have to make the decision, I don't know your circumstances.

My towel rail is of the type 1 mentioned above and I've just started moving the zone valve (whilst connecting another rad) so that it will be hot whether the heating or hot water is on. The improved pipe and cylinder insulation means the cylinder is heated infrequently and the towels stay cold.