I have a Vaillant Turbomax plus combi boiler - either the 824E or 828E, I cannot currently see which.

I have had the central heating running, and have just tried to run a bath, but no HW appeared. The boiler fired as normal when the tap was opened, but the water that comes out is cold.

When I turn the heating off and leave the boiler for a while, and then run the water, the radiators heat up - instead of the water. This happened a couple of weeks ago, but on that occastion turning the boiler off at the mains solved the problem.

From some other posts, I guess it will be the divertor valve. Might it be anything else? Am I likely to be able to fix it myself?

Many thanks, James

James M., January 2006

I have been experiencing that I had turbo hot water shower at old place .. i love it .. make me a day then new place low flow shower made me unhappy .. how can i turn on info on troubleshooting maintance or anyone on email may know about it ? shall i turn on more water pressure thru water tank boiler ?

julie Lampitt, June 2012

hi guys,
need your help please? i sort of have the same problem, please let me explain best i can.. my boiler was doing the same, only hot water when the heating was on..so i had the diverter valve fitted, worked for a while, then new problem arose..now we get heating, but when we turn on the tap for hot water, the pressure just drops on the bolier, and bolier switches off/flames goes off....so then i have to refill the boiler,swicth the flame back on and then get hot water, which i guess is ok, but if i do the same tomorrow, it happens all over again, heating comes on, switch on for hot water, the boiler pressure drops and it switches off.. what to do please anyone? plus i don't get any hot water unless boiler is switched on, even tho i had a diverter valve fitted?
what's going wrong please guys?
thanks
mac

mac, May 2012

Stuart, it does sound like your Diverter valve is at fault. I had the same problem. could only get either hot water or heating. one or the other, never both at same time. And if one was used I couldnt get the other working soon after. had to wait a couple of hours for it to cool down.

Get yourself a new Diverter valve from Ebay. I got one for about £60 inc postage. Replaced it myself yesterday. problem sorted. I was nervous about it at first but just got stuck in and found it was very easy.

Im putting together a guide on how to do it with pics so can email it to you once done if you like. Or just follow the useful guide from James M.

You can save over £300 both getting the part from ebay and fitting yourself.

Bit of a rip off what heating engineers would have charged me.

MrMan365, February 2011

Also having endless problems with not getting hot water. Boiler fires up and water tap showing on but water cold. Two diff plumbers say different things - one says domestic hot water heat exchanger needs replacing, the other that diverter valve needs replacing. Both parts very expensive so only want to fit faulty part - any ideas? Seems to be that if boiler heating radiators there is no hot water, but if heating off, hot water comes through?

stuart, February 2011

our problem is similar. the water is luke warm,when boiler has fired up, the heating is fine. also when the boiler is fired up other gas appliances e.g. gas fire gas hob, flame are reduced. Any suggestions?

kev, January 2011

the diverter valve is leaking, what do i need to do?

Paul, December 2010

we,ve had a similar problem, though I have found this normally is related to the mains pressure beng to high. turning down the mains pressure works for us most of the time. Another solution was to run the cold tap at mains pressure back up the hot tap( this is wear the kitchen mixing tap actual comes in handy) has also helped the valve resolve its strop. it beats paying £380 for a plumber to replace the valve, though this will have to happen at some point.

kirimac, November 2010

The vaillant diverter valve may be doggy at times. turning off the entire system and re-starting again has worked for me in the past. It may work for you too.

victry., October 2010

We're in the midst of a similar situation following a 4 year service when our heating engineer ran Fernox(?) through the system. When we ran the HW the radiators fired up instead and we didn't have any hot water. We've now had the diverter valve replace and the HW runs fine when the CH has been on for a while but when it's off, or just warming up from start, the HW runs cool - even though it appears to be firing. Any ideas please? We've getting really fed up with this. The engineer is coming back but we're beginning to doubt he understands the problem.

M First, February 2010

THIS IS A STUCK DIVERTOR VALVE .HEAD CAN BE REMOVED AND PIN ADJUSTED TO CLEAR .OR REPLACE ENTIRE THING

RUDGE, January 2010

It is most likely to be the diverter valve.I had the same problem.If u have an insurance ,they gonna do it for u,or if you fill confident to change it by yourself ,you can buy one from ebay,much cheaper than normal price.When u open the front panel and after the display panel secured with 2 plastic screws you will find a tag with the model.Now I have another problem. have bought a wireless thermostat/programmer and I don't know where to connect it inside the boiler

Tony Paduraru, November 2009

the diverter valve has been a problem on vaillant boilers for years,mine is the 242series and has had 3 new valves in9 years and number 4 is about to go in.Its about time vaillant made a more robust replacement.

mike stand, January 2009

it does sound like the diverter valve,you would be wise to change the micro switch at the same time.

fletch the gas man, May 2008

My system was working fine untill a changed a bathroom suite and the plummer accidently crossed hot and cold water pipes. The result was excatly what has been described above.

Once the pipes were corrected, the boiler worked at it should.

Hope this helps someone out there.

Aref Bilal, May 2007

hi I have a similar problem when the boiler is hot but if you turn the water temp to max the boiler will fire then run for about 2/3 minuets cut out but the water will be very hot .once the water is running the biloer will refire again and the water will be OK.
Did replacing the divertor valve work?
Regards

phil, September 2006

The problem u have is the same as me and it turned out to be the diverter valve not switching the flow. This valve allows hot water to flow around the central heating system or diverts the flow to the tap system when any tap is turned on.

Ron Surrey, January 2006

This is what I did. I offer no warranty that it is the correct approach. Do not try it on your own CH system. You may find it useful for what you decide to do, but do not blame me if it blows up!

1. Turn off electrics
2. Turn off service valves (located on the bottom of the boiler, having removed bottom plate).
3. Drain boiler using cock on service valve - about 6 pints comes out. Rotate drain cock until jet points at bucket. An assistant is helpful. When pressure drops to zero, shut cocks.
4. Undo nuts on diverter valve - another couple of pints will come out.
5. Unclip diverter valve from heat exchanger - drop more water.
6. Unclip electrical multi-clip (stiff & a faff, look at new valve to see where the clip is).
7. Remove old rubber washer from heat exchanger. Need a knife point/small screwdriver to lift it up; it's about 3mm from pipe end. Replace with new washer.
8. Remove old asbestos?? washers from copper pipes (they may be attached to copper pipes, or to the old div. valve.)
9. Refit multiplug. Refit to heat exchanger with new clip. Reattach to copper pipes with new washers.
10. Repressurise boiler by opening refilling valve. (If you open the CH service valves you will get a lot of air in the system.)
11. Open service valves.
12. Start up; bleed radiators; repressurise system. I guess that if you first draw off hot water, rather than starting the heating, then you limit the quantity of air taken into the system, as the air will recirculate through the boiler and be blown out through the air valve. Don't know though.

James M., January 2006

I have now spoken to the vaillant helpline. Apparently the divertor valve has a large rubber ball inside it that diverts the flow. As it ages, when it gets too hot it no longer moves, so you are stuck with no hot water.

New valve on its way!

James M., January 2006

I can describe the problem more accurately now.

If the boiler is stone cold and has not run for a while, it produces hot water perfectly well.

If the boiler is hot, then there is no hope of hot water.


Part number 252457

http://www.pricerightheating.com/Shop/ShopProducts.asp?fdShopProductShopProduct2Id=403 £74.89 + VAT

www.mjtcontrols.co.uk £77.14 +VAT + £3.50 P&P

James M., January 2006

I have been experiencing exactly the same problem as yourself. I am currently waiting for a new divertor valve. The old divertor valve motor piston is only moving in one direction. I suspect it's the motor thats at fault. If i'm wrong at least I have a spare part.
Also, when I enquired about the spare part, I was told that they have sold lots of that particular item.
The part will probably arrive next week.
In the mean time , if you have any other information I would appreciate it if you could let me know.

Roy Marshall, January 2006