Poor water pressure upstairs with combi boiler - please help

[gnubbit]

Hi,

I searched but couldn't find the info I need.

I have just had a new combi boiler installed - a Vaillant Ecotec 930. The water pressure seemed good at the kitchen sink but wasn't verified by the plumber before he installed the new heating.

The combi boiler is plumbed to the mains (not common in Ireland where I'm based) so there is no storage tank. In fact combi boilers are not used much in Ireland and I haven't been able to get any info locally.

Unfortunately the water pressure seems poor upstairs and I'm wondering if this is usual? I'm asking here because I have no confidence in the plumber; it looks to me like he did a sloppy job and the system is still not up and running properly.

I'd be really grateful for any advice - this is all way beyond my expertise and I don't even know what questions I should be asking him. When I asked him about the poor water pressure he said "ah sure that's just the way these systems are" which wasn't all that helpful

Also, I noticed that he is using the old original copper piping to bring the water upstairs to the bathroom - could that make any difference?

If I'm stuck with the low pressure do you think I might be better off with an electric shower like the Mira Sport 10.8?

Also, how should the various taps, boiler and appliances like washing machine and dishwasher be connected to the mains? I'm just wondering where things should split off.

I hope this makes sense.

Thanks,

gnubbit

 

[JohnD]

is it poor pressure at the basin taps, or just at the bath?

fill a bucket at the hot tap and see how many litres per minute you get.

see how that compares with the sink hot tap.

have the old cylinder and loft tank been removed?

 

[gnubbit]

Thanks for the reply.

I'm not at the house now so will try that with the bucket when i get the chance.

At first it seemed worse at the bath than at the basin but my husband just told me that now the pressure seems reduced at all taps including the kitchen sink. The plumber has been back doing something on the system, not sure what though!

Edit: the pressure starts off ok, then reduces after about 20 - 30 seconds

 

[simond]

I'd be surprised if you have an ecoTEC930, never seen one of those.

My guess is you've either got a 937, which is a hybrid combi, or a ecoTEC630 with an unvented cylinder. The 937 is the size of a washing machine screwed to the wall.

The flow rate (lack of) will be most evident at the bath.

Please find out what you installed and get a flow rate measurement, at the moment there is absolutely no reliable info to go on here.

 

[gnubbit]

You're right Simon, that was a typo. It's an Ecotec 937 (a monster of a boiler!).

I'll post back details of the flow rate when I get them. Which taps shoujld I measure this at? And what's the easiest way of measuring it?

Thanks

 

[gas4you]

If you have had a 937 fitted without the installer checking your incoming cold mains pressure or flow rate, i feel you might have been mislead into buying something that is not suitable for you.

You need to have 20l/min min to get the full benefit of this combi and hopefully at least 2 Bar pressure. Each storey of a property usually decrease the pressure from the tap by approx 1/3 bar.

Get a bucket of known quantity and a stop watch. ie a 10 litre bucket should fill in 30 secs. Try it at the bath hot tap.

 

[gnubbit]

The flow rate at the hot tap at the bath is 6L/min - pretty feeble!

Downstairs at the cold tap it's about 10L/min but just by looking at it, it was higher before the plumbers put in the combi. I'm not sure what could have changed.

 

[tonybhoy]

Sounds as though he has connected up the boiler to a cold water storage tank either that or you have really poor mains water pressure.

Do you live on a hill?

 

[gas4you]

Check that your main stop cock has been opened fully. You'd be surprised how many installers forget to check this at the end of the job.

 

[gnubbit]

Thanks for the replies.

Well there's no cold water storage tank (or if there is, it's against my direct orders!). The mains pressure at the kitchen tap does seem weaker than previously but not hugely.

The house is on a slight incline but it's not a huge gradient.

I'll check the stopcock - it had been turned off after a leak fr0m the new heating.

Any other thoughts?

Is there a diagram anywhere on the internet showing how this should have been plumbed so I can check this against what my plumber did?

 

[simond]

My thoughts are that if you have got 10l/m someone has been employed who couldn't find their ar*e with both hands.

An accumulator will solve this seemingly insurmountable issue, subject to the standing pressure being confirmed, and a healthy bank balance.

EcoTEC 937 has a small problem at the moment, expect to see an F81 and F91 fault.

 

[gthebuilder]

Hi I also have a vaillant 937, works quite well for me.........apart from the F81 and F91 errors....called vaillant round and they changed a number of parts and took them 3 or so visits (to be polite first 2 visits were by less experienced engineers). Since then (been couple of months) its been working fine.......until yesterday when i spotted the gremlin error again (after hot supply suddenly went cold). So ill be back on them for a solution.... frustrating that its coming to a year and i'm still experiencing F81/F91 faults.

 

[dave_h34]

gthebuilder - when was your last attempted fix? I've had F81 F91 since my 937 boiler was installed in October. Vaillant has got the frequency of the fault right down from the 'every few days' when it was first installed but it still trips out. I had a pump, 2 pcbs and 2 ntcs fitted in February but have had 2 trips since then.

 

[simond]

This problem has been affecting about 40% of our installed base of around 30 937s in different private houses.

Vaillant have been changing shift load pumps and non return valves until recently, without lasting success. It has apparently been a difficult problem to track because of the intermittent nature and the fact that some 937s don't appear to suffer from it at all.

With customer approval we temporarily downgraded the troublesome ones in software to think they are 837s while Vaillant worked on a fix, this obviously lowered HW performance slightly.

They have now isolated the problem down to the PCB; call group service for a revised replacement.

 

[gthebuilder]

Dave/Simon,

This is as ironic as it gets, picked up your replys this morning and went to wash a bowl and hey presto no hot water and behold the 937 is displaying the F81/F91 faults again.

Dave I beleive the fix of new pcb/ntc/pump was around April. Since thenthis is my second trip. I did'nt call vaillant service on the last trip as I let that one be, but this one confirms there is still a problem.....just taken some pics alongside a letter for evidence in case of any disputes.

Simon - is there anything we can do here...the unit is still under warranty and it seems that vaillant have tried all they can to fix?