Plumbing Question

[IMHO]

I do not see a forum for plumbers, so i will ask it here in General Chat.

My guest house is on top of a hill, so the water pressure is insufficient to let a few people shower at the same time. I have installed a 5000lt tank, that gets filled from the municipal supply, from where I then pump it to the house. I have a Flow Control switch on a water pump that can deliver 5 Bar. The municipal supply link to this supply from the tank, so that when the pump is out of action for some reason, we still have minimal water pressure in the house.

The problem is that lately the pressure is climbing to just below 7 bar and cause all types of havoc, like leaks and pipes bursting. I took the pump and control to the retailer today and they say I bought an overkill pump. I said the unit is faulty, as it never went over 5 bar in the beginning and they sold it to me as the right size pump. Eventually I spoke to a gentleman on the phone, the supplier, that explained to me that the problem is that the municipal supply pressure is added to the pressure supplied by the pump. The pump can deliver 5 bar max and the flow control switch it of when the pump is delivering it's max capacity. It is not looking at the pressure in bar, but rather the flow from the pump. So this is the first thing that I misunderstood and still do not understand completely. I previously used a pressure switch that switch the pump off when a certain pressure has been reached, like 4.5 bar. They however pack up every now and then and I am tired of it's problems, so I went for something else, not understanding how it works.

The supplier then said that I must isolate the municipal supply from the house, so that it only supply the tank and therefore not contributing to the pressure to the house or back pressure to the pump. So, this is the second part that I do not understand. In my mind, the say 2 bar from the municipality can not be added to the 5 bar from the pump. I reason that the total pressure will stay 5 bar. Yet, in practice it could be true what he say, as the total pressure to the house this morning was nearly 7 bar. Can someone explain this to me? If this is true, it can be that the problem was there all the time but unnoticed, because the municipal pressure might have increased lately.

I have done what he suggested this afternoon, and the max pressure now stays at just over 5 bar. I am worried however, as my son says he tried it in the past, by turning off the municipal supply and it did not help. So I will keep an eye on things and see how it develops, but if a pro can explain what is happening, I will appreciate it.

[AndyD]

Firstly I'm not a plumber so please bear with me.

Flow controllers can be a very skittish method of controlling the pumped water to your premises, especially if there's no reservior (accumulator) tank on the house side of the system.

They can cause rapid on/off cycling of the pump especially with toilet cisterns and with a dripping tap or any other low-flow condition. My first advice is to go back to pressure switch control. Pay the extra and buy a Grundfoss or Danfoss unit, it should last a lifetime. Also install a stainless steel 20 litre reservoir tank as show in the picture, this helps reduce pressure swings and pump cycling.

The high pressure at the house is most likely the council supply water. The council water pressure invariably rises during low consumption periods or plummets during high comsumption times (depending which way you look at it). I'll come back to the way you have it connected in a minute. To prevent pressure fluctuations at the house you need to have a PRV (pressure regulating valve) installed between the booster set and the house. An adjustable (1-10bar) 3/4 inch brass or stainless steel PRV would be adequate for most houses.

Finally your council water connection on the discharge side of the booster set.
Firstly it's regulations that a check-valve is installed to prevent water being pumped backwards into the council supply.
It strikes me the easiest way to provide a back-up supply to the house using the council water is to fit a second PRV at a lower setting than the PRV on the pumped side. This way you kill a whole flock of birds with one stone.
The council water will only flow if the pump has failed.
It will provide immunity to council pressure fluctuations and resulting leaks in the house.
It avoids any complicated control systems with solenoid valves etc.


I'm trying to keep this simple and I'll draw you a schematic and post it when I have aminute.

[AndyD]

Okay here's a drawing. It's not comprehensive, I didn't have time to show any dry run protection for the pump but this can be a phase angle monitor on the supply which is saimpler to install than long low level probes in the tank.

If I've misunderstood your layout just shout, I can ammend the dwg if need be.

[IMHO]

Andy, thank you very much. I will go study the drawing and come back.

[AndyD]

No probs. I ammended the dwg with some more info and added a few shut-off valves (ball valves/taps). Also you can substitute the probe set and solenoid valve at the tank for a good old fashioned ball-cock system if you like, it's simpler and less to go wrong.

[IMHO]

Andy, what would be the easiest and least expensive way to make this setup better. I agree with what you suggest, but I am looking for an easy way out, without replacing everything I got. A picture says a thousand words, so I give a link to an album with pictures, telling all. I am not placing the pictures as images here, as it will slow the thread up too much. I hope the link work!

http://s1115.photobucket.com/albums/k548/TomK59/Water%20Pressure%20System/

The main problem I have at the moment, is that the pump does not switch off, unless you close the supply to the house. That tell me I have leaks to the house and that could be anything. I can not find any burst or leaking pipes, but that is not to say it does not exist. It could also be toilets, taps etc that is leaking. When I close the supply to the house, the pump shuts off in between 9 to 11 seconds. The pressure when pumping to the house, with nothing being used in the house, is slightly higher than in the picture of the pressure gauge. The picture is taken with supply to house closed.

Would it be possible to connect the 200lt pressure tank to the setup as is and will it give any benefit? I think the pump will still not shut down, as the house is leaking?

I will probably have to chuck the flow control and buy the pressure switch you suggest. Where can one order it and will it be compatible with my current pump and other equipment?

How does the PRV work? Does it release into the line or out into the garden? I am confused with the safety device with similar name... hehe

[IMHO]

Oh, by the way. I found out last night that the pressure never climbed to 7 bar. My son made a mistake in reading the gauge. It always was as in the picture, just over 5 bar. So I must reduce to say 4 bar. Currently, when the pump shuts off, the pressure must drop to 1.8 bar before it kicks in again, which suits me fine. It is just the 5 bar that is my problem.

The flow control supplier is suggesting I restrict the intake to the pump? No idea how to do that or if it makes sense.

[AndyD]

Wow, your system is very spread out, I can see there's been quite some evolution to where you are now.

When we install this kinda system in commercial and industrial applications we basically fit all the components together in a solid manifold with stainless steel or galvanised threaded fittings, mount it somewhere solid like on a back-plate then bring all the various pipes into it. This makes for easier maintenance or fault-finding in future.

Andy, what would be the easiest and least expensive way to make this setup better. I agree with what you suggest, but I am looking for an easy way out, without replacing everything I got.

I'm sure you can re-use most of your existing components. Just lose all those HDPE fittings and get some threaded fittings to make a manifold. You can use any amount of artistic license when it comes to the size or shape as long as it's topographically correct. This one I dry assembled from bits in my workshop so ignore the copper tee's, I didn't have any s/steel ones in stock

The main problem I have at the moment, is that the pump does not switch off, unless you close the supply to the house. That tell me I have leaks to the house and that could be anything. I can not find any burst or leaking pipes, but that is not to say it does not exist. It could also be toilets, taps etc that is leaking. When I close the supply to the house, the pump shuts off in between 9 to 11 seconds. The pressure when pumping to the house, with nothing being used in the house, is slightly higher than in the picture of the pressure gauge. The picture is taken with supply to house closed.

The constant pump run isalmost certainly that damn flow-sense control. Even a minute water flow thru a toilet cystern ball float valve will set the pump running. Like I said above.....skittish. Ditch it before it drives you insane and fit a pressure switch.

Would it be possible to connect the 200lt pressure tank to the setup as is and will it give any benefit? I think the pump will still not shut down, as the house is leaking?

Yes, install the pressure reservoir tank, with a pressure switch it will stop the pump short cycling. (With the flow sensor I doubt it will change anything.)

I will probably have to chuck the flow control and buy the pressure switch you suggest. Where can one order it and will it be compatible with my current pump and other equipment?

The further you chuck it the better. Any good irrigation supplier should have pressure switches. Get a 0-6(ish) Bar 'break on rise' type and buy a good one.

How does the PRV work? Does it release into the line or out into the garden? I am confused with the safety device with similar name... hehe

A PRV is a device that sits in-line with the water flow. Regardless of the pressure coming in, it supplies a constant pressure going out. The pressure can be adjusted, you need two with a range of 0-10Bar on the output. It doesn't dump water anywhere...I think you're thinking of a geyser expansion valve which is sort of similar but also different.

Oh, by the way. I found out last night that the pressure never climbed to 7 bar. My son made a mistake in reading the gauge. It always was as in the picture, just over 5 bar. So I must reduce to say 4 bar. Currently, when the pump shuts off, the pressure must drop to 1.8 bar before it kicks in again, which suits me fine. It is just the 5 bar that is my problem.

Setting the pressure switch is a 2 stage operation. It has 2 adjustment screws, one for the range and one for the differential (hysteresis). It should come with instructions, if not get advice from the suppliers. I would aim for pump-off at 4 Bar and a differential of 1 Bar max so pump-on would be around 3 Bar.
I would set the pumped-water PRV at 3 Bar and the council-water PRV at 2 Bar.

The flow control supplier is suggesting I restrict the intake to the pump? No idea how to do that or if it makes sense.

He's talking kak. If you restrict the pump on the suction side it can cause it to cavitate which can cause a whole new basket of problems. It certainly won't solve any of your existing problems.

[daveob]

@Andy

I've been following this thread with extreme interest for a number of reasons.

Without wanting to hijack the thread, could I ask you to please explain a few things for me (looking at your pdf drawing):

1. what is the purpose of the (blue) bypass line from the Council Supply to the 'Lower setting' PRV ?

2. I don't see any output from the Pressure Tank, so don't understand why it's there. Surely it should have some in/out flow ? Or is it used to simply store pressure. If so, wouldn't the pipes going to the building contain the same pressure ?

3. is the PRV ( just above the pump ) there to control the pressure supplied to the building, irrespective of the pressure delivered by the pump ?

4. I assume the dotted line from the pressure switch is there to indicate that the drop in pressure at the switch ( caused by opening a tap in the building ) would cause the pressure switch to register a drop in pressure, and would send an (electronic ?) signal to the pump to activate ?

[AndyD]

1. what is the purpose of the (blue) bypass line from the Council Supply to the 'Lower setting' PRV ?

Hi Dave, that pipe is the 'back-up' water supply in case of power cuts/pump failure. The PRV is set lower to make it redundant if the system is at pump pressure. I included it in the drawing because IMHO stated in his OP;

The municipal supply link to this supply from the tank, so that when the pump is out of action for some reason, we still have minimal water pressure in the house.

Thinking again about it that PRV could in fact be set marginally higher than the PRV on the pump output. This would then mean as long as the council pressure is equal to or higher than the PRV setting then the pump won't run. If or when the council pressure drops below the setting of the pressure switch then the pump will take over supplying the house. This might be a better set up, it would make the life of the pump longer.

2. I don't see any output from the Pressure Tank, so don't understand why it's there. Surely it should have some in/out flow ? Or is it used to simply store pressure. If so, wouldn't the pipes going to the building contain the same pressure ?

There is a single hose to the pressure tank, water flows into and out of the tank via the same hose. The tank has an internal rubber bladder which is pumped up to around 1 Bar with air. When the pump runs it charges the tank and the bladder compresses. When the pump is off and water is being used at the house the pressure tank will supply this water until the bladder expands again to a point where the pressure drops sufficiently for the pump to restart. It just provide a buffer reservoir of water under pressure to prevent the pump rapid cycling.

3. is the PRV ( just above the pump ) there to control the pressure supplied to the building, irrespective of the pressure delivered by the pump ?

Yes, the PRV would supply the house with a constant pressure regardless of the pump output pressure being higher.

4. I assume the dotted line from the pressure switch is there to indicate that the drop in pressure at the switch ( caused by opening a tap in the building ) would cause the pressure switch to register a drop in pressure, and would send an (electronic ?) signal to the pump to activate ?

The drawing wasn't the greatest, it was a bit of a rush job. The dotted line was just to associate the pressure switch with the pump it's controlling. The pressure switch is mechanical, it has a set of electrical contacts that make when the pressure drops below a preset point which starts the pump. The contacts then break when the pressure rises above a preset point which stops the pump.

[IMHO]

BTW, Andy, my parts is ordered and I should get it this coming week, so be prepared for the questions... hehe

[AndyD]

Great. I actually forgot aboth this thread, good luck and let me know how it goes.

[IMHO]

AndyD

I got the parts this morning, but it looks like I have been conned with the pressure switch. I repeatedly asked for Grundfoss or Danfuss and was assured it is a Grundfuss. Now the item arrive here and it is a Telemecanique!

What do you make of it?

[Martinco]

As far as my experience goes, the Teles are not that bad !!

[AndyD]

Yep it's looking good to me as well, Telemechanique should do the job just fine. Nice photo by the way