Lots of problems with Vaillant Boiler, not sure what to do

[money_penny]

Hi, I've been reading this forum all day hoping to find a simiar problem and solution to mine, the only thing is whilst I have found lots of things about the individual problems I can't find anyone who has them all at once! Sorry for the long post but I want to include everything.

To start at the beginning we moved to our house 2 years ago, there was (still is) a Vaillant turbomax combi boiler installed. The bathroom and kitchen were in need of some updating and at the time there was no shower so as a temporary measure we attached one of those shower things you attach to the taps and the pressure was so good it used fly around the bath like a hose if you let go.

Then we had new bathroom installed and changed layout of bathroom too, we had a mixer shower installed off the mains. This is when we started to notice a few problems.

First of all the power in the shower since installation is completely miniscule, to the point where i struggle to wash shampoo out of my hair. We had the guy back who then said we needed a pump, but I was cautious of this because some say you shouldn't put them on combi systems but also because it was never like this before.

Then a few months later the hot water started to get a bit dodgy, and has got slightly worse over time. Early mornings about 7am we always seem to be able to get hot water for a shower (even if it is miniscule flow) but later on it is often luke warm/cold. Most times i can fix this by turning the shower off, then switching boiler off then on again and we get hot water through.

Then sometimes during the day our hot water is intermittant at all taps (we have mixer taps on bath, bathroom and kitchen sinks) - more often cold than hot though, in fact i feel lucky if i get piping hot water during the day/evening. I have however discovered that if I turn the tap to the hot setting and have it on very slow flow through the tap then the water is nice and warm, if i turn it up full blast it goes cold then returns to hot again when i turn back to slow flow.

As if this isn't enough, the pressure in the boiler occasionally creeps up and up till sometimes i have to let some water out to reduce the pressure (it goes up to 3 - in the red on the gauge).

We did get a new plumber to come and take a luck (we weren't getting anywhere with our usual one). He said it could be the diverter valve or the heat exchanger, his advice though was to replace the boiler completely for a woucester greenstar 28i junior. Other plumbers I have rang (but haven't looked at boiler) say this seems extreme.

I really don't know what to do for the best and am in need of some good advice. Also dont know if this is an issue but apparantly the gas pipe I have supplying boiler starts at 22ml then reduced to 15 ml before it enters the boiler.

Please help!! Thanks

 

[bengasman]

Definitely not a pump and definitely not replacing it with a junior 28i.
First guess is a clogged up heatexchanger or faulty sensor.
Check that both hot and cold are mains fed by trying to stop the flow form the basin taps by pressing your thumb on the spout. Open the tap slowly if you don’t want a shower when you do this.
I can not see how the different times of the day are of influence, probably just coincidence.

 

[money_penny]

That is great thank-you. Sorry to appear stupid but what should i look for when i stick my thumb over the tap that would indicate that it is mains fed, and if it's a mixer tap do i turn it to cold and test then to hot and test.

 

[bengasman]

Only test the hot and cold basin tap.
Not stupid, forgot to mention that you won’t be able to hold the water back if it is mains, but will be able to block the flow easily if it is tank fed.
Don’t try it on the mixer as it will not physically separate the hot and cold.

 

[Gasguru]

The hot tap will be off the mains. The cold tap should be off the mains but cowboys frequently leave it plumbed off the old storage cistern (if that was the setup before a combi went in).

Unless your mains pressure is a little low you can't normally stop the water with your thumb. If it's relatively easy to stop the flow, then the water is from a storage cistern at low pressure. Most showers require balanced ie equal pressures for hot and cold to function correctly.

Is the boiler a Turbomax ie it has a black lower panel and green knobs

or a Turbomax Pro/Plus ie small digital display in the center and for small buttons below...they are very different boilers.

Have you measureed the flowrate from the hot tap? You should be getting at least a full standard 10 or 12 litre bucket per minute. If not the boiler isolating valve, flow limiter, inlet strainer, flow restrictor or plate heat exchanger (rarely) may be blocked or not fully opened.

Most Turbomax's will heat around a bucket per minute to bath temperature, a flowrate higher than this and the water will not get sufficiently hot.

The 3 Bar pressure reading is not good...read the FAQ's about re-charging the expansion vessel.

The early Turbomax (green knobs) was the last reasonably well built Vaillant and is way better than the Worcester Junior.

The Turbomax Plus has several design faults but I'd still say it's better than the Worcester.

 

[Agile]

Whilst we all have ideas this lady has had two plumbers and neither seems to know what they are doing!

Tony

 

[money_penny]

Thank you all for your replies, I must have a turbomax pro as I have the digital display and four buttons as you described. I have tried the thumb over the tap and I can't hold back the water. I will try to fill a bucket of hot water when i get in tonight to test the flow rate, and let you know how I get on.

 

[weareleeds]

A common fault on these is the diverter valve. To test make sure htg is turned off & allow pipes to cool down turn on hot tap & feel 22mm pipes leaving boiler, If one of these is hot then you will probably have the earlier valve which will need changing as most of the blr performance will be directed to rads hence cool water

 

[bengasman]

Whilst we all have ideas this lady has had two plumbers and neither seems to know what they are doing!

Tony

Are you surprised that 2 plumbers did not have a clue, or that ONLY 2 didn’t?

 

[Agile]

I was surprised that NEITHER of her two plumbers had any clue!

 

[money_penny]

Thanks to everyone for their replies. I did as you said to see if it was the diverter valve and it certainly seemed to be. So, having lost all faith in plumbers after my experience with the two previous ones I decided to take out boiler cover with vaillant, who sent someone today to replace the diverter valve. I now have hot water, at any time of the day, at any flow rate, which is fantastic... I am very grateful for your sound advice as I may have ended up getting whole new boiler!!!

My next question is about the miniscule flow in the shower, this has not improved following replacement of the diverter valve (though I have to say I wasn't expecting it to). I tried to see how full I could get a regular bucket in one minute, the bath tap filled the bucket in a minute, however the shower filled only about 1/6 of the bucket in a minute??

 

[Bahco]

Try taking the head off the shower and see if you get a lot more flow.

 

[money_penny]

Just tried that and got much more water through in a minute (about the same amount of water in a minute as I did from the bath). So clearly the shower head is the problem, will a new shower head be better and if so how do I know which one to go for so that I don't get the same problem. Also I was hoping the flow would still be a bit better, but is this the best I can expect??

 

[Terrywookfit]

Larger bore hoses are availlable,
Try a plumbers merchant for a decent head !

 

[money_penny]

I still fear that despite a better shower head the flow (although better) will still not be that strong, is there anyway to improve the flow to the shower?