Shower alternating hot and cold - boiler or shower problem??

[DanNZ]

Hello,

I'm after a bit of advise. We are off-shore landlords, renting the flat where we used to live in London.

We have an agency looking after the tenancy, and all has been pretty good.

Last week, we received an email from the agency, saying the tenant was having an issue with the shower, and they were sending out someone for a look.

We didn't hear anything for a few days, so I contacted the tenant. She said that someone had been around and said there was a problem with the pump and thermostat in the shower (it's a panel type shower with additional jets) and often it's cheaper to replace the whole shower!!

Now, I checked with the tenant, and the problem she was having sounds the same as one which we noticed occassionally while living there. The shower alternates hot and cold and hot and cold - etc! It is run off a combi boiler (Vokera) and I have had the shower partially off the wall before. I'm pretty sure there is nothing there except a couple of valves (mixer and selector valve for different shower options).

When it used to do it, you could actually hear the boiler clicking off (it was in a cupboard behind the shower), and you'd have a second or so before the shower went cold, then you'd hear the gas fire up again and it would warm up. I believe the fault is in the boiler??

I let the maintenance company know my thoughts and concerns. They are still adament that the fault is the shower, and it's thermostat and have since sent a quotation for over £900 to replace the shower!!

What do you think, could the shower be creating this fault - my thinking is that it isn't and the person who checked it out doesn't know what they are talking about

I did find some forums of people discussing similar "hot, cold, hot, cold" issues with the Vokera boiler, where replacing the thermisters solved the problem. I have asked the agency to send a service engineer to service, and repair the boiler but they are suggesting that would be wasting our money!!

Appreciate any help on this before I go back to the agency...

Thanks,
Danny

 

[DP]

Dan, your shower could be an issue. Get the tenant to check if a hot tap elsewhere gives constant hot water. If water delivery elsewhere is at a constant temperature, get tenant to run the shower with a cold tap also running elsewhere. If now shower delivers tempered water at desired temperature, issue is excessive cold water pressure or problem into shower unit.

You will be well advised to dump the people who are advocating repairs as you DO NOT have a pump to run the shower if the boiler is a combination boiler

Which Vokera do you have. If the boiler is around 15 years old, it could be a Flowmatic, at 10 years old could be Excel, less than that Linea. But then again, Vokera made many boilers. For each model it could be a different component giving you similar results. It is unlikely to be a thermistor (none fitted in the Flowmatic)

Combination boiler will generally either have a plate to plate heat exchanger or a composite heat exchanger that heats radiators or heat water when desired. System sediment and dirt often blocks the heat exchanger to result in erratic hot water delivery that your tenant is experiencing presently. This problem is not common to just one brand (Vokera) but almost every boiler that has not been installed correctly (i.e. system properly cleaned when boiler installed and the treated with suitable chemicals).

You do not need blind panic stricken repairs but a methodical check to pinpoint the defect and then take action.

 

[DanNZ]

If now shower delivers tempered water at desired temperature, issue is excessive cold water pressure or problem into shower unit.

From the above, are you implying that after a positive result from that test, it could still be either the shower - or the boiler?

So, excessive cold water pressure into the shower could cause the boiler to shut down / fire up (you can hear it doing that) - and it could still be the shower at fault? How could it be the shower - is it to do with the mixer shutting off the hot supply and turning it back on for some reason?

The boiler is only 5 or 6 years old. I think it might be the Linea?

I'll ask the tenant to try those suggestions and see where we get too!

Thanks very much!

 

[bengasman]

Sounds to me that agent is either completely clueless, or trying to pull a fast one and earn some money off you.
As a lot of agents have plenty of time on their hands, they have spent some of that on creating a substantial list of trades people they can call out at a moment's notice and will work for very little.

£900 at this moment is ridiculous.
It also sounds much more likely to be a boiler fault than a showerproblem; most likely it is corrosion/limescale debris in the heat exchanger, in which case I would estimate half of what you have been quoted at the very most, and I live and work in London

 

[DanNZ]

OK, I've sent a few questions to the tenant and let her know that I'll arrange for an independant Plumber / Boiler Service technician to visit.

I'll get them to service the boiler and try and diagnose the issue.

If they decide the shower needs a new mixer (is this also called a thermostat?), do you think it would be possible to retrofit something off the shelf from a plumbing store?

Here's a picture of the shower...

Untitled

• DanNZ
• 20 Jul 2009
• 1

[/img]

 

[DanNZ]

Just had some responses:

* While the shower is running, if you turn on other taps in the flat (hot
or cold) does it affect the shower temperature? Yes
* Does it alternate hot and cold EVERY time you use the shower, or is it
intermittent? It used to be intermittent but in the last couple of months
its every time.
* Does it alternate hot and cold when the temperature is up full hot in the
shower? Not tried, but will let you know
* Does it alternate hot and cold on any other taps in the flat? no
* When it is alternating, does turning on a cold tap in the flat stop it doing
that? Not tried, but will let you know
[/b]

 

[DanNZ]

Hi again,

I've just had a local plumber / boiler repairer look at the problem. Here are his comments:


"I have been to your property in Croydon and I had a good look at various possible causes. One of the tests that I performed was to measure the flow rate of water passing through the shower hose whilst set to hot & cold individually & l also tested the kitchen sink.
The flow rate results were the same at all outlets, 2.5 litres a minute on the hot outlets & 8 to 9 litres per minute on the cold. The boiler is repeatedly shutting off as a result of this low flow rate through the boiler, this is most likely due to scaling up, lime scale that falls out of hard water when heated. If you would like me to I can, I believe change the heat exchanger & several other components, sensors filters & so on to return the flow rate to the specification that the boiler was designed to provide, subject to the mains water pressure that is supplied by your local water authority. This is expensive but it will be more expensive to change the whole boiler! During my investigation I also discovered a leak in the boiler on the pump housing. I will need to change this part to prevent water loss & the constant need to top up the boiler, also adding lime scale to the heat exchanger. Sorry for the bad news!

All in all it would I believe be better in the long run for you to change the boiler. It is the more expensive option in the short term, but I honestly believe that a nice new economical condensing modern combination boiler will be a good long-term investment & should you wish to sell the property it will have added value to the sale & buyer appeal. Please let me know what you would like me to do for you & then I can get some prices for you."

What do you think? I'm surprised a 6 year old boiler needs to be replaced?!

I've asked for him to quote on the 'minimum' to solve the problem, and on options for new boilers.

Danny

 

[Agile]

It seems like yet another nupty plumber who wants to do a nice profitable boiler replacement.

Its clear he has no idea of how to repair boilers!

The Linea is a modern boiler constructed from common components which is TOTALLY repairable.

This is the problem you will face. Its difficult for you to find a competent person who can repair any boiler. They just want a £2000 job to replace a boiler when a repair woulf be about £200.

I expect he went there free of charge in the hope of getting a new boiler job.

We dont make any visit free!

Tony

 

[gas4you]

Sounds to me like the plate HE needs to come off and be de-scaled/cleaned and any inlet filters checked for blockages.

8-9 litres on the cold seems very low any way, and could indicate a problem with the incoming mains

 

[DanNZ]

Here's a reply to some of my questions (my questions in BOLD, reply in Italics):

I remember the tenant saying the hot and cold fluctuation was only happening on the shower - not on other taps in the flat. If the heat exchanger was so calcified to be restricting the flow to the shower, would you not expect to see the temperature variation on other taps? The temperature fluctuation was happening as early as 2 years from new (occassionally). Would you expect the heat exchanger to be blocked after such a short time?

It is very possible in some circumstances depending on things like boiler design, flow rate, water hardness & usage, (not limited to these examples) I have however found today during further investigation that there is a part on the inlet to the heat exchanger that has been known to cause reduced flow rate on the boiler model in question! I can strip down this part of the boiler & replace this part only @ £60 + labour.

It is possible that the fluctuation happens on the shower only, because of the restrictions in the shower head. Water flows much more freely through an open tap. It is also likely that it happens on the taps as well but it is les noticeable due to the amount of time they are used compared to the shower. But that said, this is 80% science & 20% speculation. I don’t know until I strip the boiler down whether it’s blocked up or not, but my experience & that of others I have spoken to leads to that conclusion. Other causes could be a blockage in the pipes themselves or even natural resistance through the boiler. But I have measured the flow rates accurately at hot & cold outlets & the cold supply is defiantly higher & that’s a large drop across the boiler.

What is the impact of not replacing the pump housing?

Well, it is leaking a reasonable amount, possibly something like 100 to 200ml per day (I have not measured this) going by the frequency of the drips. The casing has some rust on it which will only get worse reducing the integrity of the casing & becoming very unsightly in time. The dripping is caused by water leaking from within the pump housing, so reducing the water content within the boiler. Your tenant will need to be constantly refilling / toping up the boiler as time goes on. The resulting constant injections of fresh water into the central heating side of the boiler will regularly coat the heat exchanger in freshly supplied lime scale!! All in all the impact will be an accelerated decline of your boiler. The heat exchanger is split inside so you have a central heating pathway & a hot water pathway. It is less likely in normal operation for the central heating waterways to become calcified as they are designed to be filled with fresh water much less often. Cost of housing £80

I would like to minimise the cost of any repairs (obviously being sensible about it). I can't really see why a 6 year old boiler should need replacing. Could you provide a quotation for:

A modern combination boiler commonly gives around 10 years of economical use. During this time you would expect to start spending money on it at around 4 years onward. It is really down to so many circumstances, as I have already mentioned. Also quality of the boiler makes a big difference, it’s like buying a Ford fiesta or a Mercedes Benz. I would expect very different outcomes to everyday wear & tear. Boilers like cars do a lot of mileage, but even then it is possible for a fault to arise on the “better model” first!

Minimum repairs to get the boiler sorted: Parts + labour £240
a 'cheap' replacement boiler £1600
a 'good' replacement boiler £2500 including work on increasing the size of the gas supplier that will be needed.


Any comments? I think I'll be doing down the cheapest route!! By the way, he's already charged for a boiler service @ 75 pounds. I guess it still doesn't guarantee that there are no issues with the shower!

 

[Agile]

My comments are that he is very good at writing and quite good at charging but can cleverly make it look as if he knows whats wrong and what needs to be fixed.

However, he has already been to see the boiler but still apparently has no real idea of whats actually wrong.

Oddly, I did see some text sent on to me by a customer, which was written in a very similar way, a couple of years ago.

Tony

 

[bengasman]

£75 for a proper service is reasonable, the rest of it is dubious.
If you go for another boiler, I would strongly suggest you spend some time finding a good installer, but I doubt a six year old boiler is a write off.

 

[tamz]

Check filters to shower or partial blockage of showwer valve.If hot inlet filter or valve is partially blocked this may cause hot flow through shower to drop below level to keep boiler alight.

 

[Agile]

Tamz, exactly who are you expecting to check the filters?

 

[tamz]

Anyone who wants to!