Residential water pressure design - Help

[Peter Neubert]

Hi All

I am about to build a house and I have the following challenge that I would like some help with:

I live in a country where the water supply is at best inconsistent, furthermore we suffer from periodic power cuts, particularly in cyclonic period after which we can be without electricity for days.

Consequently most residential water systems are designed with: a) an underground tank, to accumulate water and ensure stable supply - typical size around 10 cubic meters.

b) a smaller (2-500liters) roof tank, feed from a pump somewhere between the roof and the underground tank. This roof tank then provides the pressure and water for the house.

Problem: With the roof-tank solution the water pressure is far from what we are used to in the developed world, and problems often arises when multiple outlets are used at the same time. I would like to have a nice constant pressure, comparable with what one will find in Europe or the States. At the same time, it is important that I have water even when I am out of electricity.

I remember from my childhood, us having a pressure tank used with a well and providing a nice pressure in all of the house - this is not used much in this area for the reasons above, SO.. I was thinking - would it be possible to design a system giving the best of both worlds

- in line with the following:

A) Underground tank as above B) Pressure Tank feeding the house Cold water pipes and the C) Solar Water heater - I live in the tropics so this can easily provide 99% of hot water needed. D) Roof tank, this would then be used when there is no electricity - probably connected to the rest of the house plumbing incl the Solar water heater via a set of non-return valves to avoid backflow from the higher pressurised house system. Once the electricity is off, and the pressure is down, the roof tank would then provide water for the house. I was thinnking it would be fed directly from the pressure tank and the level controled with a simple floater or something similar.

One problem I can foresee here is that the roof tank risk holding the water for long periods, and thus the freshness could not be guaranteed

- I was therefore considering feeding external water points (garden etc where the pressure is not as critical as it is in my shower) from here to give at least some circulation in the roof tank. By the way, we dont drink the water from the taps.

As I have absolutely no experiences with designing these kind of system - I would like to hear from anyone who could comment on my "design" and any good ideas/advice would be greatly appreciated.

Thanks Peter

[Harry K]

Simple booster pump feeding from the roof tank with a checkvalve between the pressure tank and roof tank should do the job. The system would work under the 'house' pressure as long as there was electricity, then feed from the roof tank through the pump/pressure tank during no power periods.

Roof tank - booster pump - pressure tank - house

This, of course, relies on the water being able to flow -through- the booster pump when it isn't running. Never tried that so not sure if it will.

Harry K

[Joe Bobst]

Sounds like you want to redesign the wheel. Before you do, if you live in any sort of a community, take a notebook and do a survey of all the types of existing systems you can find in tour area. Take these data to a competent architectural/engineering firm and work with them to develop the plan you find most suitable. You have to live with the system a long time so it's important to get it right. The internet isn't going to be much help unless you find someone who has solved the identical problem in the exact way you want it. Whatever, good luck.

Joe

Joe

[Harry K]

After re-thinking that there is a better way.

You have a ground tank with a pump of some sort feeding a roof tank with feeds the house.

If the pump will pump to 40 or 50 psi, and the roof tank can stand that pressure, all you need is a pressure tank.

Roof tank I I-------------Pressure tank----- house I I Pump/ground tank

This assumes that: a: you have a float valve that stops the input to the rooftank when it is full b: There is a check valve either in the pump or at least below the "T".

The pressure switch (normally installed at the tank but doesn't have to be) will be more convenient if it is one without the need to override it when the power comes back on. Most have an override you hold until pressure comes back up. Mine doesn't have that and will start the pump as soon as power is restored.

If the tank can't take the pressure then you are back to installing a booster pump/tank using my original diagram. You can install the pump in that in a bypass loop that doesn't require the roof tank to feed through the pump during power out.

_pump_ Roof tank __check valve__/________\___house/pressure tank

Of course this is shade tree engineering. A professional may have better solutions.

Harry K