Vaillant Ecotec 28 - Low hot water flow at taps

[eccoboy]

Hi folks, I'm after a bit of advice on the above boiler. Essentially the central heating all works spot on but the hot water flow rate is really poor from all three hot water taps.

What could be the problem? I'm competent enough and have replaced pcbs pumps and diverter valves on an alpha boiler before but need a bit of help!

I'm thinking that the heat exchanger may be clogged up - am I on the right track?

Any help greatly appreciated, cheers Ben

 

[Agile]

Wonderful how you decide that its really poor! Based on what?

You need to MEASURE the flow rate and the boiler is designed for about 11 litres per minutes!

Your title also implies that you don't understand the difference between pressure and flow.

Tony

 

[eccoboy]

Hi Tony, thanks for your reply, appreciated. Good point on the title, I'll amend that! Cold water pressure is fine, I'll check the flow rate in litres per minute and report back....
Cheers Ben

 

[eccoboy]

Hi, measured the flow rate at each hot water tap and it's only approx 4 litres per minute....

 

[Agile]

That is seriously low.

There is clearly something reducing the flow.

All you can do is to ensure the isolation valve where the cold enters the boiler is fully on.

There are two possibilities, a flow limiting part which might have become clogged somehow or lime scale could have blocked the water side of the plate heat exchanger.

You can remove the plate and theoretically check and clean it but that is somewhat advanced DIY.

Tony

 

[eccoboy]

Many thanks Tony, I can check the inlet for sure and I'll do this tomorrow. I'm not in a hard water area (Yorkshire's finest!) but is it possible that the heating side of the plate heat exchanger could be perfectly fine whilst the hot water side is blocked up? It's just that the heating works brilliantly, really efficient to warm up.....
Once again, thanks for your help, appreciated.
Cheers Ben

 

[Agile]

Its the plate heat exchanger we are talking about.

That's only relevant when providing hot water.

That needs to be clear to get the full hot water flow.

Sometimes when water mains are replaced a lot of sand gets into the water main and blocks the plate.

Tony

 

[ScottishGasMan]

Assuming your cold water runs much faster than this? you should be getting about 9.5/10litres min on the hot water side.

Its very unlikley the plate has any involvment in it in a soft water area, that much sand would have killed the flow switch by now if that was the issue, however its not to say the inlet to the boiler is not clogged, under the boiler there is the inlet pipe for the cold water, will have a flat faced screwdriver operated quarter turn valve (dont mistake this for a similar valve and pipe found on the gas inlet to the boiler!) firstly ensure that is open, if it is, close it and undo that connection to the boiler and there should be a small metal filter in there with the flow limiting washer, could remove them and see what you have.

other than that its looking at possible gate valves/stopcocks on the cold supply to the boiler being accidentally turned down that could restrict the flow to the boiler but not the cold running taps (again assuming they have a significantly higher flow rate)

 

[eccoboy]

Hi folks, update: isolated the mains water, drained via the hot water tap, removed inlet valve and sure enough a massive load of debris was blocking it. Looked to be a combination of grit and corroded steel. Emptied it out, flushed it through, blew it through both ways to ensure it was clear and refitted. Flow rate is now spot on, beautiful
Thanks very much for your help and hope this thread helps lots of others out there.

 

[Agile]

Well done!

 

[Elle69]

I have the same problem right now.
This evening, I filled the bath for my son, then about 1/2 hour later I noticed the house was getting cold and rads were cooling down.
I first went to my boiler (Vailant Ecotec) to check the pressure. It was a little low - at about 1 bar so I opened both valves under the boiler to let some air into the system. Normally, you can hear it gush in, but I could only hear a very faint sound. The needle moved ever so slowly barely reaching 1½bar, then the needle seemed to sort of flicker... as if restricted air flow... I don't know...
Anyway, heating on again, then I tried to run the hot water tap - no water coming out, completely dry!

Could this be the same thing as above guys, a blocked inlet valve?
If so, can you confirm my understanding of the above please...
I turn water off at the mains: run taps off around house (although, there's no water coming out of the hot taps here!); and turn off the boiler... Am I then safe to undo this valve to see if it's full of rubbish?

 

[ScottishGasMan]

Chances are if you have filled system using a built in filling loop (2 grey handles under boiler) then the Right hand one which is part of the valve shown above is still in the filling position (it stops mains water entering the hot tap pipe when in filling position) open a hot tap, then open and shut the grey handle on the above shown cold water valve and see if any water starts to come out tap, if not it may be that the grey plastic handle has worn off at the brass connection, if so remove grey handle (small star screwdriver) and use flat blade screwdriver to rotate the brass valve to correct orientation again

 

[Elle69]

Thank you SGM! You're a marvel. I've sorted it and have hot water again!

Out of interest, is it a difficult job to fit a new knob to the joint/valve, or does the whole assembly need to be changed?

Thank you x

 

[ScottishGasMan]

No you can buy just a pair of handles on their own. just the one screw holding them on
https://www.plumbnation.co.uk/boile...gV-DppXi7cKWmqCMBkuOFQXb8CZvyFJgaAg7GEALw_wcB

 

[Elle69]

Ah that's great, thank you! It's not often that a fix is so easy... and cheap!