Vaillant boiler - diverter valve?

I have a Vaillant ThermoCompact boiler which has started to play up. It seems "reluctant" to produce hot water sometimes. This first happened last winter, but only very intermittently, and only for the shower which is upstairs. Now it's more common to either get the shower not running hot, or to have it go cold half way through. Usually a few seconds turned off will get it going again, but sometimes it takes a couple of goes.
I was wondering if it's a low pressure thing - the shower head is the highet outlet in the house and I never get the problem on any of the other taps. Anyway, the boiler is in good condition, so I'm hoping it will be servicable? Does it sound like I'm right, and is it a DIY job?
Cheers,
John
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On Sun, 06 Aug 2006 14:06:10 -0700, aboleth wrote:

The thermocompact is a system boiler not a combi boiler. So problem with the HW would lie elsewhere. However the description of your problem sounds much more like a Turbomax+ which does have a diverter valve.
The valves are sub 100 and easy to change if you have some plumbing experience and can read the manual. Any attempt to Fix this valve will cause you to have a fully broken boiler.
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Ed Sirett - Property maintainer and registered gas fitter.
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Ed Sirett wrote:

I decided it must be a thermocompact purely on the basis that the previous owners left a load of paperwork and a manual for one. It's certainly an on-demand hot water provider, does this mean it must be a turbomax? How does one find out, it doesn't have any model number I can find.
I have a (very) little plumbing experience. Does the job require soldered joints, if so I'll probably have to get a pro. I've only worked with compresion fittings.
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On Tue, 08 Aug 2006 06:43:17 -0700, aboleth wrote:

I presume this boiler say Vaillant on the front. It mostly white enamel and beige plastic. The knobs are probably turquoise but might also be beige.
No soldering is needed to make this replair, but you need to be able to drain the boiler and refill it and get the air out.
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Ed Sirett wrote:

You're being very helpful, as I seem to remember you were with a previous boiler of mine! Would you mind looking at these 2 photos to see if you can tell me what I've got. When I opened the bottom a label fell off with a few numbers on. the last of which were 37/97 which I take to mean "made in the 37th week of 1997" so perhaps it's not as new as I thought. All looks in good condition though.
http://qurl.com/js1nm http://qurl.com/77497
Where would I find the instructions to make the repair?
Cheers
John
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On Wed, 09 Aug 2006 12:37:54 -0700, aboleth wrote:

You've go a Turbomax combi (without the '+'). Its a VUW 824e I think. It's probably one of the last units made of this model.
Problems with the HW on the model are more likely a split diaphragm on the water flow detector. This is a considerably more difficult part to change. It's in the big round brass part on the second picture.
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Groan! Thanks for clearing up the model for me. "Considerably" sounds like I should not really be attempting this myself.
Thanks for your help
John
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aboleth wrote:

Sorry to resurrect an old thread...
Just been quoted 220 + vat to replace the diverter valve on our Turbomax. This seems like a lot of money given that the part seems to be available for 60 + vat, so we told them no thanks. Am I right, or is this the kind of money we're likely to pay? Also worried that Ed suggested it was more likely the diaphragm, is there any way to tell which problem we have?
Cheers
John
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On Thu, 07 Sep 2006 03:54:07 -0700, aboleth wrote:

IIRC this model is a turbomax (no plus). It uses a diaphragm to detect water flow and operate the diverter valve.
The diaphragm seem to be the weak link in this model (and all boilers which use this system). The complete diaphragm/diverter valve could be replaced as a whole.
The local boiler spares shop will charge more than the online price. The job will take a couple of hours. There is a possibility of call backs so the fee is reasonable.
I charged 200 to replace a diverter valve on a t/max+ the other day. 100 for the part and 100 for me to get out on Sat am, get the part and fit it. The customer was _grateful_ rather than quibbling, quibblers find I'm too busy to give up chunks of my w/e for them.
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I take your point, but in fact you have been more helpful here for nothing than these guys were in person. They were uninformative, and they wanted more on a thursday then you charged on a saturday, so I'm pleased I turned them down.
I quite fancy giving it a go, but I don't have a service manual or any set of instructions at all, even generic. Do you know of such a resource? It looks like the job woud be:
1. Drain system. Turn off gas, power and mains water. Run taps to let out any residual water. 2. Remove electrical connections from valve. 3. Disconnect water connections from valve (any particular order? precautions?) 4. Reverse 3 and 2 with new valve (PTFE tape on joints?) 5. Refill, add inhibitor. 6. Turn everything back on, cross everything, try the hot water and heating.
Is this right, or have I missed out 7 (redfaced phonecall to plumber)?
John
Ed Sirett wrote:

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You might check if it's scale (or rust flakes, or a partially closed or blocked valve) that's restricting the flow to the shower head -- it sounds like it may not be the boiler, because it's only a problem on the one outlet.
Thomas Prufer
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Thomas Prufer wrote:

It's now actually started to effect all the taps, sadly.
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