I have a pumped shower in the upstairs bathroom, pump installed in the airing cupboard adjacent to the HW cylinder. We also have unregulated solar HW which easily provides water at 80 C ++ in the summer months.

This damages the shower pump (2 so far), causing pulsing and cavitation, which is a pain for those taking a shower.

To fix this, I intend to install a Salamander TMW (it's a Salamander CT-50 pump) - http://www.plumbworld.co.uk/salamander- ... 3603-22165

The install diagrams for this indicate that it needs a dedicated 22mm supply from the header tank, which will be a complete PITA to arrange.

I also need to fit an S-Flange to the tank as none is currently fitted and, whilst I'm at it, replace the immersion element that is currently U/S.

I'm a fairly competent DIY plumber and *really* want to avoid waiting weeks and then shelling out lots of cash to get a professional to do this, but it's easily the most complex job I've tried, hence need for some advice.

Immersion Element first: I assume I just need to unscrew the existing one, wire up and screw in the new. Is that correct? Any obvious dumb mistakes to avoid? (Yes, I can do the 'leccy stuff - part P and all that...)

Next the Flange: Same question really. Presumably I just drain down the HW, disconnect the existing pipework at the top of the tank, screw the flange into place and reconnect the pipework to the top of the flange? Any common errors here? (Obviously I need to re-route the existing shower pipework to the flange, rather than the existing T, but that's all visible and easy.)

Lastly the TMV... Salamander recommend their own one (they would, wouldn't they!) but like I said the 22mm feed from the loft will be a pain. I have loads of CW head-pressure (about 2.5M from tank-top to header tank); so can I just tap into the existing supply in that case, or do I *really* need the separate feed?

If the Salamander TMV does require the dedicated feed, can I use one like this instead? http://www.screwfix.com/p/honeywell-4in ... id=1182090

The only differences I can see are the HoneyWell is rated to 46 C output rather than 55 C and has non-return valves.

- Does it matter that the TMV has non-return valves? Why?
- Given that we like fairly hot showers, will the decreased input temp for the pump cause a problem? (I'm thinking that the thermostatic shower will probably not draw so much cold when the hot is only 46 C rather than 55, which might mean the flow is quite low on the cold side of the pump...)

Lastly - all this started because of the problems caused by over-hot water. Since we're now running off the boiler again, the pump seems to be behaving better and I'm rather hoping not to have to buy another new one. What should I look out for in case it has been permanently damaged by the heat? Leaks? Obvious distortion of the housing? (Neither present afaics) Anything else?

Thanks

Tim

Follow-up...

(still need help!)

Reading the install instructions (http://www.plumbworld.co.uk/link/1/pwsm0031_10404_t.pdf), I find a couple of interesting points.

First this on p8: "The hot connection must be via an approved side or top entry flange except for CT 50/75 and NP 50". (My pump is a CT50)

Then (p11) the diagram attached here, suggesting that as the CW head is over 1.5 M I can take the hot feed straight off the vent.

So that suggests I don't need the S Flange... Or is that still recommended, even though it is optional?

Tim

There's only one way to connect a pump, and thats MI best practice if you want it to last longer than 10mins.

Essex, or an S flange, Essex being the preferred method, but a pain for a DIYer.

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One last thing... That Cold feed from the tank; World and Dog say *never* to feed the shower off the same cold feed as the HW cylinder inlet...

But I seem to have a single (22, perhaps 28mm) drop from the header tank currently feeding Bath, 2x Basin, 2x Toilet Cylinder AND Shower.

In that case should I *really* be worried about T-ing it off again to feed the TMV?!

Tim

Nothing, and I'll repeat it, Nothing should be tee'd into the cylinder cold feed.

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Thanks Scruff - I know this should be done perfectly, but it's an old house and starting-over is not really a viable option - airing cupboard looks more like the boiler room of HMS Belfast than most normal houses as it is!

Fitting the S-flange is no big deal - I just want to avoid over-complicating matters unnecessarily.

Can you help with my other queries: Should I worry about using a TMV with non-return valves (and why?) and should I be concerned about the relatively lower temperature of the HW feed to the pump if I use the alternative TMV?

Ah; and why should I worry about stuff being tee'd to the Cylinder feed?

Relief, I am finding out more than I ever wanted to about the plumbing here.

So using a torch I was able to trace back cold feed from the basin in the bathroom. Turns out this is actually fed from the mains supply directly (and so I assume are all the other cold taps), not from the cylinder input as I thought. Confusion because the mains supply is hidden behind the cylinder drop in a corner of the cupboard, so almost completely invisible.

The shower, however, HAS been installed as a tee on the cylinder input. Probably because that was easier than running a new drop (previous owners were definite bodgers).

I suppose I should change that, but would still like to understand why...?

Also, I noticed in the loft that the outlet from the tank to the cylinder is directly under the inlet - some diagrams suggest that's a no-no, why is that?

(Thanks, btw, for answering these - Looks like I should be able to get an NVQ at least once I've got my head around all this stuff!)

Tmv with non return valves should make any difference.

You could starve the cylinder and implode it.

High risk of back flow and contaminated water, e.g. Legionella.

Connecting the outlet under the inlet means you could have aerated water going into the cylinder etc.

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Thanks for all the assist - between you and the nice folks at Salamander & Screwfix I think I know what the solution looks like now.

New 22mm drop from the tank to feed the shower. With a T off that to supply the cold feed to a HoneyWell TMV. New S-flange on the tank and a replacement immersion element for good measure.

Oh, and a weekend in the loft by the look of it!

Sounds fun Good luck

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