Hard water and new boilers in Northampton and Milton Keynes

There is one number that decides whether scale protection is a nice extra on your boiler quote or something the manufacturer expects to be there. It is 200 parts per million of total hardness.

Northampton and Milton Keynes are both comfortably the wrong side of it, which makes this one of the few things about a boiler installation that is genuinely local. Below is what the water here is, what the manufacturers say about it, and the three things it should change on your quote.

What the water here actually is

Both towns are supplied by Anglian Water, and Anglian Water's own water quality fact sheet is unambiguous: all of the water in the Anglian Water region is classed as hard to very hard. The reason is geology rather than treatment. The ground across the region is high in chalk, the water passes through it, and it dissolves calcium carbonate on the way.

Northampton appears on the map in that fact sheet inside the hard to very hard band, and so does the whole of the surrounding area. This is not a postcode lottery where one street is soft and the next is not. If you live here, you have hard water.

Anglian Water publishes a hardness figure by postcode on their site, and it is worth pulling your own before you talk to an installer, because it is the piece of evidence that decides the rest of this article.

Source: Anglian Water, Water Quality Fact Sheet 11: How hard is my water; Anglian Water, Hard water

Why 200 ppm is the number that matters

It is the threshold the boiler manufacturers themselves use, and they use it in their installation instructions rather than in their marketing.

Ideal Heating's installation and servicing manual states that in hard water areas where mains water can exceed 200 parts per million total hardness, a scale reducing device should be fitted into the boiler cold supply, within the requirements of the local water company. Worcester Bosch put it slightly more softly in their instructions, saying that where temporary hardness exceeds 200 parts per million, consideration may need to be given to fitting a scale prevention device and the advice of the local water authority should be sought.

Two different manufacturers, the same number. And in an area where the supplier's own literature says the water is hard to very hard everywhere, that number stops being hypothetical.

Source: Ideal Heating, Logic Code Combi ESP1 installation and servicing instructions; Worcester Bosch, Greenstar 8000 Life installation and maintenance instructions

Scale and sludge are two different problems

This is the part that gets muddled in almost every article on the subject, and it costs people money because they buy one product and think they have covered both.

Scale is a hot water problem. It forms on the side of the boiler that your mains water passes through, which on a combi is the plate heat exchanger that heats your taps and shower, and on a cylinder system is the coil inside the cylinder. Scale comes from the hardness of the incoming water and it is dealt with by a scale reducer on the cold mains feed.

Sludge is a heating problem. It is corrosion debris circulating in the sealed loop that feeds your radiators, it has nothing to do with how hard your water is, and it is dealt with by cleaning the system and fitting a magnetic filter and inhibitor. Manufacturers reference the relevant code of practice for that directly in their instructions.

A magnetic filter on the heating return does not protect the hot water side from scale. A scale reducer on the cold main does not protect the heating side from sludge. In this area a properly specified job has both, and they are two separate lines.

Source: Worcester Bosch, Greenstar 8000 Life installation and maintenance instructions

The water softener trap

Plenty of houses around here already have a water softener, and the reasonable assumption is that it solves the boiler problem too. It does not, and in one respect it can make things worse.

Ideal Heating's manual is explicit that the use of artificially softened water is not permitted. Worcester Bosch's guidance on cylinders is similar in spirit, distinguishing between scale reduction and softening. The reason is that ion exchange softening changes the chemistry of the water in ways the appliance is not designed around, so a softener is a solution for your kettle and your shower screen, not a substitute for a scale reducer on the boiler feed.

In practice that means the cold feed to the boiler is normally taken before the softener, with the scale reducer on it. If you have a softener and nobody has mentioned this, it is worth raising before the boiler goes on the wall rather than after.

Source: Ideal Heating, Logic Code Combi ESP1 installation and servicing instructions

It is on the paperwork that validates your guarantee

The strongest argument for taking this seriously is not in the sales literature. It is on the commissioning checklist.

The Benchmark section at the back of an Ideal installation manual, which is the document an installer completes at commissioning and which manufacturers require for the guarantee, has a line for combination boilers asking whether the installation is in a hard water area above 200 parts per million, and if so what type of scale reducer or softener has been fitted.

So the question gets asked either way. It gets asked on the day the boiler is commissioned, on the form that goes in the back of your manual, and the honest answer for this area is yes. It is better for that to be a line on the quote than a conversation in your kitchen with the boiler already fitted.

Source: Ideal Heating, Logic Code Combi ESP1 installation and servicing instructions

Three things to check on your quote

None of these require you to know anything technical. They are just questions with right answers.

• Is a scale reducing device included on the cold mains feed, and which one. Manufacturers name specific approved products in their own instructions, so there is a correct answer rather than a vague one.
• Is system cleaning and a filter included on the heating side, separately from the scale reducer. Two problems, two products, two lines.
• If the house has a water softener, where is the boiler cold feed being taken from. It should not be from softened water.

Why this changes what quotes look like here

If you are comparing prices in Northampton or Milton Keynes and one is lower, this is one of the first places to look before you assume you have found a bargain. Scale protection and system cleaning are exactly the sort of items that vanish from a quote to make the headline number smaller, and neither of them is optional in the sense that matters, which is the sense the manufacturer's instructions use.

The wider point stands beyond this: the appliance is the most comparable line on a boiler quote and the least likely reason two prices differ. What differs is everything around it, and in a hard water area the water is part of everything around it.

Getting it priced properly

Local installers already know the water here and most of them price for it without being asked. The value in knowing the number is that you can tell, from the quote alone, which ones did.

If you want prices from Gas Safe registered installers who work in this area every week, we can arrange that.