Boiler repair or water softener?

Hello, this is my first post so I don't know if I can set up a voting poll on the forum.

We have been thinking of getting a water softener to soften the mains water, but now our boiler (Baxi Combi 105e) is playing up. The hot water goes cold. It eventually heats up again or we can switch the water off and wait a minute before turning the tap on again. The engineer is 90% sure that it is because the heat exchanger has scaled up and it needs replacing. We do live in a hard water area.

My question is which opiton would you choose?

OPTION 1
-----------
Replace heat exchanger. Parts + labour = £186

OPTION 2
-----------
Get the water softener we want to get any way (£500+) which will gradually dissolve the limescale. But does the boiler have to take unsoftened water due to the pH?


Hajj

You will need to check with the manufacturer's instructions (or phone them) to know whether the boiler will take softened water.

Even if you install a water softener, it will take ages for the softened water to dissolve existing limescale, and if the heat exchanger is fairly well scaled, there may not be enough circulation to dissolve it at all.

I'd change the heat exchanger, then install a water softener if:

a. The boiler will take it.
b. The slightly reduced cold water pressure won't compromise the system

Replacing the hex is pointless; fault will repeat and probaly sooner rather than later if the hex is the problem.
Does the water go hot cold hot cold etc in more or less constant cycle of around 20 seconds, or irregularly at much longer intervals/

Hello. Thanks for both replies. Yes, I have heard the boiler stopping and starting without getting really fired up at approx. 20 sec intervals, like you say.

But I think it depends on the flowrate of the hot water. I turned the shower down from the beginning an could have an uniterrupted shower.

When the kitchen hot tap was on full then the hot water went cold and then started to heat up again after a minute.

So the hot-cold cycle can be different.

Testing for this kind of fault must be done by single unmixed tap; mixers and especially thermostatic are no good.
Kithcen tap or basin tap with flow on maximum i.e. more than 10 litres/min. Boiler dhw thermostat on max.

Unfortunately you have not said where you are.

Its very rare for plate heat exchangers to get lime scaled even in very hard water areas unless there is a boiler fault or a dripping tap.

That price for fitting a new plate seems a bit high. We would clean it for £136.

I suppose he has given you a free diagnosis and in that case as you might fix it yourself his price is higher. I always charge to diagnose a fault.

It is very likely that the problem is caused by sludge rather than lime scaling unless you live in Bracknell or Buxton! So a water softener is unlikely to be required specifically for the boiler.

Water from an ion exchange water softener is not particularly good at dissolving lime scale so I dont think you should expect a boiler repair from that. Particularly as its more likely to be sludge blockage anyway.

Tony

The fault has been detected on two-lever mixer taps in th ebatthroom and kitchan, not just the one-lever shower mixer. Flowrate of hotwater was high. Cold water was off.

Plumber said £65/hr and h/ex about £80, although I saw some for about £50 online. He said cleaning it with acid will just ruin the delicate fins on th h/ex.

I am in Greater London. Just tested the hardness on the cold water from the mains, (it was a fresh supply, not standing) it is 340-380 ppm which makes it very hard.

Although the problem has been present for a year, since we moved in, it only developed significantly recently. I was a way for about 10 days, so perhaps the standing water hardened on the h/ex. There is scale coming out of the pipes, but the engineer said everybody has that. I have had a twin-tech magna clean installed for about 6 months now. but I am guessing that is on the heating circuit and not the hot water circuit.

I spoke to the sales person at Harvey's who said installing a water softner will lead to the dissolving of scale in the pipes and boiler etc. in 6 months, worst case scenraio. I spoke to someone more technical at Monach and he said it will take 1yr or more (again, worst case scenario).

Any comments?

Hajj

I am surprised that you managed to measure the hardness in your water so accurately! What did you use to do that?

Nothing you have said changes what I have said previously.

Tony

Hajj said:

Plumber said £65/hr and h/ex about £80, although I saw some for about £50 online. He said cleaning it with acid will just ruin the delicate fins on th h/ex.

Click to expand...

If it is a blocked hex, it has little to do with water hardness.
Replacing the hex is only a temporary solution.
Acid will do no harm whatsoever to the hex.

Sounds like you need a better plumber, or more accurately: a RGI who is a breakdown specialist.

Hajj said:

Plumber said £65/hr and h/ex about £80, although I saw some for about £50 online. He said cleaning it with acid will just ruin the delicate fins on th h/ex.
Any comments?

Hajj

Click to expand...

Oh dear!

If he is right then I must ruin the delicate fins on about 30-40 h/ex each year.

I always thought that I was saving money for the customer! I did not realise that I was ruining them.

Odd though that no one has ever complained after I have cleaned theirs!

Got a testing reagent from eBay to test the water hardness. There are a few different kits including test strips too.