He Asked If Soft Water Would Eat His Pipes. The Answer Was in the Pipe Schedule.

This is a note about an objection I get in meetings whenever a softener appears in one of our quotations, and about the fact that the answer to it turned out not to be a chemistry argument at all. It was a question about what the pipes in the building are made of.

The job was a commercial building here in Cebu with a kitchen heavy enough that we were pricing a softener alongside the wastewater plant. The deal is live, so I am not naming it. I have written about two other pieces of that same job already and this is a third thing, not a restatement of either: once about a paragraph we deleted from our own quotation, which is an argument about drafting, and once about why the crust in a hard-water grease trap is soap rather than grease, which is the chemistry of the kitchen. This one is the objection the owner's side raised to the softener itself, and why we now answer it by asking for the pipe schedule rather than by arguing about water chemistry.

The objection, stated fairly

It usually arrives in roughly this form. Soft water is aggressive. Hard water lays down a protective film of scale on the inside of a pipe, and that film is what stops the pipe corroding. Take the hardness out and you strip the film, and now the water is in direct contact with bare metal, and you have traded a scale problem you could live with for a corrosion problem you cannot see until something leaks inside a wall.

I want to be clear that this is not a stupid objection. It is the standard objection, it is in the literature, and it is the reason water utilities think about the balance of their finished water at all rather than just about how clean it is. Somebody who raises it has read something. The part I would push back on is not the mechanism. It is whether the mechanism has anything to act on in the building we are standing in.

So I asked what the risers were made of

That is the whole of it. Before I say a word about calcium carbonate I want to know what the water is touching on its way through the building.

In practice, in Cebu, the answer is polypropylene. I do not think any building here is going to use galvanised iron for its riser pipes. Within the building it is almost always PPR, and it has been for long enough that the only buildings where I would expect to find metal risers are genuinely old ones. That is a field observation rather than a survey, and I will say below what I do when I am not sure. But it is the working assumption I bring to a Cebu building, and so far it has held.

If the riser is PPR, the objection answers itself, and it answers itself twice over. There is no protective scale layer for soft water to strip, because the pipe never needed one. And there is nothing underneath for the water to attack if it did, because polypropylene does not corrode. The mechanism in the objection requires a metal surface that was being protected by a deposit. Neither half of that is present.

This is a small thing and it changed how I handle the conversation completely. The answer to a chemistry objection was a materials fact, and the materials fact is cheaper to establish than the chemistry. Anybody can look at a pipe.

The one place metal does appear, and why it does not matter

There is galvanised iron on these sites. It is on deep well columns and on rising mains. I am not pretending it is not there.

What matters is where it sits in the order of things. The well column and the rising main are upstream of everything. They lift raw groundwater out of the ground and deliver it to the cistern or to the header, and a softener sits downstream of all of that, treating a feed that has already been through the metal. The GI only ever sees raw water. Whatever hardness that raw water carries, it is still carrying it when it passes through the pipe that the objection is about.

So installing a softener cannot make the well column's life harder, because the well column is on the other side of the softener. That is not a design subtlety we engineered in. It is simply the order in which the components of a water system have to be arranged, and once you draw the line and mark where the softener goes, the question stops being arguable.

Where the exposure actually sits

Having said all that, I do not think the right conclusion is that the saturation index does not matter on these jobs. I think it matters and that everybody, including us, has been looking for it in the wrong place.

The thing on these sites with a large wetted surface made of calcium compounds is not pipe. It is concrete. Cisterns, ground tanks, sumps, and on the wastewater side every chamber we pour. Cement paste is held together by calcium hydroxide and calcium silicate hydrate, and water low in calcium and low in alkalinity is, in principle, able to take calcium out of it. That is leaching rather than corrosion, it is slow, and it shows up as softening of the surface and sand coming loose rather than as a pinhole.

I am going to mark that clearly as reasoning rather than measurement. I have not pulled cores out of a cistern and compared a softened tank with a raw one, and I do not know anyone locally who has. What I can say is that if there is a saturation-index exposure on a Cebu building fed by a softener, the concrete is where I would go looking for it, and the pipe is not. That is the opposite of where the objection points.

What we do about it, which is less than you might expect

Three things, none of them dramatic.

The first is that on the jobs where we put a softener in, it serves a defined feed, not the whole building. On that commercial building it was the kitchen, because the kitchen is where the hardness was doing damage worth paying to stop. The cistern upstream still holds raw water. The tanks and the pipework that are not on the softened branch are not in the argument at all, and the softened branch is short and mostly plastic. Softening a feed rather than a building is cheaper, and it also happens to cut the exposed concrete surface down to almost nothing.

The second is that we were already building the concrete to hold water, which is a stricter requirement than resisting a mildly aggressive water. A tank built the way we build tanks has a dense mix and detailed joints, and the reason for that is water retention rather than chemistry. I have written out the pour sequence we put in every civil quote and the way the chambers are blocked together with shared walls, and the same workmanship that makes a tank hold water is what makes its surface durable. We get this one largely for free, and I would rather say so than claim credit for it.

The third is that the softened stream on these jobs mostly does not end up sitting in concrete for long. It is used, it becomes wastewater, and by the time it reaches our chambers it is carrying everything a kitchen puts into it, which is a long way from being a calcium-hungry water. The clarifier detail we now repeat on every job has never shown us a problem I could put down to this.

What we do not do is add a remineralisation or alkalinity-adjustment step to a building softener in order to answer the objection. That would be buying equipment and a monthly chemical to fix something I have not demonstrated exists, and it would also make the softener exactly the liability the client was afraid of. One of our standing rules is never to let an outcome depend on a chemical that may not be on the shelf locally, and that rule exists because we have watched it bite.

Why this changed how we ask, not just how we answer

The useful part of all this was not winning the argument in the meeting. It was realising that the fact which settles it is a survey item.

So the pipe material went onto the survey list, next to the pipe diameter and the number of floors and the kitchen's operating hours. We ask what the risers are, and if nobody knows we ask for a photograph of a riser at a landing or in the pump room, which takes somebody thirty seconds. We are not asking in order to warn anybody about anything. We are asking because the answer decides whether there is a subject to discuss, and because a question costs nothing while an argument costs trust.

That is the same discipline we use for asking for an influent result, which almost nobody has, and for pulling the characteristic parameters off our own list by industry rather than asking an owner to diagnose his own effluent. Ask for the data item. Do not ask the client to agree with your conclusion before you have the data.

It also means that when the answer does come back as metal, we are not caught out. We have a real question in front of us at that point and it goes in front of the owner properly, with the arithmetic rather than with adjectives, in the same way everything else in the design basis does.

The buildings where I would not give this answer

I would not give it in a genuinely old building. If the risers went in when galvanised iron was the normal choice, the objection is live and the mechanism has something to work on, and the honest answer is that we need to look at the pipe before we promise anything about the water.

I would not give it where the softener is being asked to serve the whole building rather than a feed, because then the softened water is touching everything, including the cistern, and the exposure I described above stops being negligible.

And I would not give it where somebody has already seen leaks. A building with a history of pinholes is telling you something about its pipework that my general assumption about Cebu construction does not override. At that point the softener is not the interesting question.

Where this does not transfer

This is a local observation doing most of the work, and local observations travel badly.

The pipe assumption is about buildings I have been inside, in and around Cebu, over a reasonable number of years. I would not carry it to a city whose construction history I do not know, and I would not carry it to an industrial site, where metal pipework is chosen for reasons that have nothing to do with what the plumber down the road stocks. In both cases the answer is the same as it is here when I am unsure, which is to go and look.

The concrete argument is reasoning and I have said so. If somebody has measured it properly on a Philippine site I would like to read it, and I would change this post rather than defend it.

The feed-not-the-building point rests on the hardness being concentrated in one place, which is true of a kitchen and not true of, say, a hotel where the complaint is scale in every bathroom. There the scope is different and so is the answer.

And the whole discussion assumes the softener was worth installing in the first place, which is a separate question with its own arithmetic. We size one on service flow rate and exchange capacity, we keep it on equipment we can support after the sale, and if the hardness comes back low enough that the kitchen was never going to suffer, the right answer is not to sell one. The softener goes into base scope when it is removing a problem, and we treat to the level the building actually needs rather than to the level we could reach.

If you want the rest of how we work before you talk to anybody, the compliance page sets out the discharge limits as they are, the price estimator will give you a band without a conversation, and what we have built is on the site. If you already know roughly what you need, start from getting an STP, or from the water treatment side if the problem is the incoming water rather than the outgoing. The four questions I would ask before signing apply to us as much as to anybody else, and if you already own a plant, operation and maintenance support and our consultation service are separate things you can buy without buying a plant from us. We work across Cebu and the rest of the Philippines.

And if a softener has turned up in somebody's quotation and you are not sure whether the objection applies to your building, send me a photograph of a riser. You can book a free 15-minute consultation and we will know inside the first five minutes whether there is anything here to worry about.