Building Construction, Renovation, Maintenance & Advice

Plumbing Mistakes In Water Supply Systems

"A Wet Dream"

“My water's smelly” he said.
“Too much information” I said.
“Oh no not me, if I stank like that I'd get myself put down. I mean the water from my taps at home, stinks it does.”
“Near the septic tank?” (the first question to ask).
“Well actually the smelly water is only one problem. I had a pump put in, you know, to increase the pressure, didn't make any difference. I can't understand it, it's a big pump.”
“That's strange.”
Well actually that's not all.” he said rather sheepishly.
“Not all?”
“No, I er, I had a water heater put in.”
“That's nothing to be embarrassed about.”
“Well, er, I have to admit, this cold showers thing is all very character building but I had a recurring dream about a nice hot shower.”
“That's allright, may I be so bold as to ask - is it satisfying?”
“I don't really know.”
“You don't really know?”
“Every time we switch the water heater on the power cuts out. We have never been able to use it.”
“I'd better take a look.”

What I found at Henry's nice new house was rather disturbing,

This was obviously one of those benevolent jobs where the contractor considers the customer ordered the work purely for the charitable purpose of circulating some money and alleviating poverty (his own), the idea that the customer actually wanted a working hot water system probably never occurred to him.

It is difficult to imagine how anyone could get it so wrong and then charge money for it. We will look at water systems in general and what happened to Henry and perhaps we can all be a bit the wiser.

Let us start at the beginning which is usually the well or more often these days the bore. Most household water systems in Indonesia follow the same basic pattern as follows:

Water is pumped from a well or bore or, if available, comes from the town water supply (PDAM – Perusahaan Daerah Air Minum).

In simple systems the water may be supplied directly from this pump to taps and toilets around the building. You turn on a tap, the water pressure drops which switches on the pump which then pumps water from the bore directly to the tap.

In many houses (particularly older ones) the well pump supplies water to a tank which is at some high point, very often on a steel or concrete tank stand or perhaps on a concrete slab built into the roof of the building. Water can now be fed by gravity to the taps and toilets around the building. The advantages are that you get a nice even water pressure and if there is a power cut you still have water (until the tank runs dry). A typical tank for an average house will be about 1,000 litres in capacity (note this is a metric ton of water – a lot of weight) and made from either low grade stainless steel or plastic.

There is a float valve in the tank which switches the well pump on now and again to top up the tank.

If the building has two floors or long runs of pipe from the tank to the taps then often another pump is installed to boost the water pressure. This is simply a pressure pump and a fairly small pump will do the job. Turn on a tap and the pressure pump switches on.

Many people these days want hot water. To do this we have to take a branch off the cold water supply pipe AFTER the pressure pump (if there is one) which then goes to the water heater and from there to the hot taps (obviously not to the toilet unless you like that sort of thing). Water heaters may be “storage” (they have a tank in which the water is heated and then stored until use) or “demand” which means the water is heated as it passes through the heater.

Storage heaters are usually electric or solar while demand heaters tend to be gas. You can buy electric demand heaters and you will often see them being peddled by smooth talking salesmen in shopping centres but, take care, these usually require high electric current to heat the water fast enough, or else they provide luke warm water - gas is a better bet for demand heaters.

Water heaters can reduce the water pressure, particularly if you have hard water and the pipes “fur” up. If you don't already have a pressure pump you may need one to push the water through the heater to give reasonable pressure in your hot taps.

Now as you can appreciate none of this is rocket science (come to think of it have you ever thought how difficult it must be to shave in the space shuttle? Does the water go down the plughole clockwise or anticlockwise?). So let us return to Henry and see what went wrong. He has a four bedroom, four bathroom house plus a kitchen and laundry. All water was supplied directly from the bore pump. He wanted hot water installed. The contractor installed a water tank in the roof, a 500 litre electric storage water heater and a very large pressure pump.

Mistake 1
A branch was taken off the cold water pipe to feed the tank AFTER the supply to the cold water taps. Even though he has a water tank all the cold water taps still drew water directly from the well pump losing the advantage of having the tank.

Mistake 2
The pressure pump was about 5 times as big as it needed to be, cost about Rp 2.5 million when Rp500,000 would have done the job, not only for the hot water but for the whole house. This pump was so large that the water “pulsed” badly and took a whopping 800 watts to run.

Mistake 3
The water heater was 500 litre (I've never seen one so large in a domestic house before) when 100 litres would have done the job. The large heater had a 3 kilowatt heating element. As soon as it was switched on the lights in Kerobokan prison went dim and the PA system at Sanglah Hospital crackled into life to warn everyone that Henry was planning to have a bath. Henry's electrical supply couldn't cope and cut out. Henry had never had hot water!

Mistake 4
Finding the hotwater connections obviously proved too difficult for our highly intelligent “trades”men and the final installation had hot water to only two guest bedrooms. Unfortunately these were the two rooms that seldom get used. The laundry, kitchen and the two bedrooms used most had no hot water connected.

As a final problem, because this new system couldn't be used the roof tank was left stagnant and became green and pretty nasty.

I suspect this work cost Henry a lot of money for a system that simply didn't work, mind you he can feel good that he made a very generous contribution to his contractor's poverty alleviation fund.

To give you some basic guidelines:

  1. The most common well or bore pumps are Grundfos pumps 550 watts (¾ horse power) to pump a 30 metre head or 750 watt (1 horse power) for a 40 metre head. The head is the height between the SURFACE of the water you are pumping from to the highest point you are pumping to. With a pressure tank such a pump should cost about Rp3 million.
  2. The well pump should pump water directly to the water tank if you have one.
  3. If you have a pressure pump this would normally be only a small pump (perhaps a 200 watt ¼ horsepower Shimizu pump) situated on the outlet from the water tank. If you have a large house you may need more than one. Such a pump should cost around Rp600,000.
  4. If you have a water heater or heaters these would normally be situated on a branch off the cold water pipes after the pressure pump. Storage water heaters come in 3 commonly used sizes – 50 litres for kitchen sinks, 80 litres for a single bathroom and 100 litres for 2 bathrooms. If you wish to supply 4 bathrooms use two 100 litre heaters this will reduce the electricity draw particularly the peak load surge as the heaters switch on.

It has to be said that every house is different, some situations can be unusual and may require variations. If there are variations you need to start asking why. Just be aware that over specification can allow a contractor to make more money from a job but can actually create more problems than it solves.

“What about the smelly water?” I hear you say. Well we have talked about that before and I am sure we will look at it again soon.

Copyright © Phil Wilson 2009
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8 February 2017 Copyright © Mr Fixit,
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