Surging water pressure

[3STTW]

I moved into my new house about a year ago and there's a water pressure issue that's been bugging me since day one. Basically, when you turn on a faucet or shower the pressure slowly dwindles to nothing and then demand pump kicks in for about 10 seconds and then the pressures declines, repeat, repeat, etc. If there's more than faucet/shower running at the same time the effect is even worse.

 

The main cause of this is that the storage tanks, demand pump (and the pressure switch) are located in an out-house 15m away from the main house, there are 3 upstairs bathrooms which will inevitably create their own back head pressure even when they're not in use and will obviously influence how the pressure switch works. Yes, I know, a sh!tty design but the pipes are all underground/walled-in and I can't relocate them without a serious amount of reconstruction. We also have a central water heater located downstairs which adds to the misery - it means I can't install a header tank in the attic without screwing up the hot/cold mix at the faucets.

 

I wonder if you guys know some way to remedy the problem to both increase the water pressure and even out the surging effect? 

[Crossy]

Task A. check if the pump pressure tank is waterlogged.

 

In a nutshell (we can do better with a photo of the pump / pump type).

• Close the water tank outlet valve.
• Power off.
• Remove the drain plug and air inlet from the pressure tank.
• Wait whilst the water exits the pressure tank.
• Replace both plug and inlet.
• Open water tank outlet valve.
• Power on.
• Test.

Note some pressure tanks are pre-loaded with gas and cannot be re-loaded if they leak, new tank needed. Others have car-tyre type valves so you can pump them up with a compressor rather than just let the atmosphere do the job.

 

[JetsetBkk]

It seems to me that your pressure switch is not sensitive enough to detect the small drop in pressure when you open a tap. Have you tried replacing it with a new one?

My tank and pump are at the back of the house, but I have no problem with the pump switching on and off. The house is a single story.

Actually, the biggest problem I had was the pump switching on and off too quickly. But that was fixed by draining the pump's pressure tank to get some air into it which acts to smooth out the pressure delivered.

Edited March 6, 2021 by JetsetBkk
to > too, ballast > pressure

[VocalNeal]

10 minutes ago, Crossy said:

(we can do better with a photo of the pump / pump type).

 

What he said

[3STTW]

There's the demand pump on the left side, ignore the sprinkler and pool pumps top and right.

 

I have no idea how these things work but I'm guessing you guys will do the necessary.

 

And thanks for your quick replies!

[Artisi]

28 minutes ago, 3STTW said:

There's the demand pump on the left side, ignore the sprinkler and pool pumps top and right.

 

I have no idea how these things work but I'm guessing you guys will do the necessary.

 

And thanks for your quick replies!

You have the best, Grundfos, looks like it has done a fair bit of work. 

My suggestion is get in the local pump guy to view it, there are a number things that need checking, the airpressure in the tank needs to be checked and at the correct pressure coupled with the pressure switch setting - not difficult if you know how to do it, a minefield if you don't. 

[JetsetBkk]

1 hour ago, JetsetBkk said:

Actually, the biggest problem I had was the pump switching on and off too quickly. But that was fixed by draining the pump's pressure tank to get some air into it which acts to smooth out the pressure delivered.

 

Sorry to quote myself but my neighbour - at the back of my house - had a serious "water-lock" problem with her pressure tank and pump. Her pump would come on and off twice a second - quite noisy while she was using water. I couldn't contact her as her house has a high garden wall around it and she didn't answer my knocks on the gate. After a few weeks the noise stopped.

 

Then about a year later it started up again. This time I waited until she had gardeners in to cut her grass so I went round to see her.

I told her about her pump problem and she apologized for the noise! I said I wasn't concerned about the noise but her pump would probably fail if she didn't drain the pressure tank to let some air in. She had no idea what I was talking about but did add that about a year earlier she had to have the pump replaced after it stopped working.... ????

[3STTW]

47 minutes ago, Artisi said:

You have the best, Grundfos, looks like it has done a fair bit of work. 

My suggestion is get in the local pump guy to view it, there are a number things that need checking, the airpressure in the tank needs to be checked and at the correct pressure coupled with the pressure switch setting - not difficult if you know how to do it, a minefield if you don't. 

 

Okay, thanks for the advice. In the meantime I'll try and learn how these things work and have a crack at it myself, I've had a parade of 'local guys' doing stuff and every single job has turned to rat sh!t. My wife now has a ban on calling the 'local guy'!

 

 

 

[3STTW]

Again, thanks for your advice guys. I've just found the pressure meter behind the water pump and I'll take some video tomorrow with the pump at standby and then with a faucet running.

 

 

[Artisi]

The Grundfos tank is air over water via an internal bladder, it is possible the bladder is faulty, ie leaking, if this is the problem the pump can hunt on and off during operation. The bladder needs to be pre-charged to a certain pressure depending on the model and in conjunction with the pressure switch the pump will shut off at "x" pressure and restart at "y" pressure.

Somewhere in my junk pile I have the data for bladder recharge pressure and pressure switch detail, will have a look for it and post if I can locate it. 

 

Don't get your local fix-it -all to look at it, call Grundfos and ask who to use in your area. 

Edited March 6, 2021 by Artisi

[Pogust]

You can easily set the on/off pressure yourself. Take the lid off the black box on the side, inside you will find the pressure switch. It might even be instructions inside the cover how to do it. You set the max pressure and the difference between max and min. I have the same pump and set mine to work between 2 and 3,5 kg pressure.

 

[Crossy]

13 hours ago, Artisi said:

The Grundfos tank is air over water via an internal bladder, it is possible the bladder is faulty, ie leaking, if this is the problem the pump can hunt on and off during operation.

 

We have this pump too.

The bladder has a slow leak (after 10 years) and the tank gradually becomes waterlogged leading to symptoms very like our OP is describing.

There's a Schreider (car type) valve under that grey cover on the top of the tank.

I will get around to replacing the beast one day but for now I turn everything off, open a tap and pump the tank to about 30 psi (wait until the water stops coming out of the tap before topping up the tank).

It lasts about a month until I need to do it again.

 

Now, where's that round-tuit?

[Artisi]

32 minutes ago, Crossy said:

 

We have this pump too.

The bladder has a slow leak (after 10 years) and the tank gradually becomes waterlogged leading to symptoms very like our OP is describing.

There's a Schreider (car type) valve under that grey cover on the top of the tank.

I will get around to replacing the beast one day but for now I turn everything off, open a tap and pump the tank to about 30 psi (wait until the water stops coming out of the tap before topping up the tank).

It lasts about a month until I need to do it again.

 

Now, where's that round-tuit?

Maybe worthwhile pumping in some of the magic gunk used on leaky car tyres, might seal it for awhile until round-tuit arrives. 

[Crossy]

5 minutes ago, Artisi said:

Maybe worthwhile pumping in some of the magic gunk used on leaky car tyres, might seal it for awhile until round-tuit arrives. 

 

Oddly enough I was thinking just that about 30 minutes ago ????  Tanks are not repairable so no harm in trying.

 

Great minds think alike (or fools seldom differ).

 

A new tank is about 3k Baht on Shopee.

[Artisi]

4 minutes ago, Crossy said:

 

Oddly enough I was thinking just that about 30 minutes ago ????  Tanks are not repairable so no harm in trying.

 

Great minds think alike (or fools seldom differ).

 

A new tank is about 3k Baht on Shopee.

Think on grundfos tank the bladder comes out thru the bottom of the tank, worth checking 

[Artisi]

1 hour ago, Pogust said:

You can easily set the on/off pressure yourself. Take the lid off the black box on the side, inside you will find the pressure switch. It might even be instructions inside the cover how to do it. You set the max pressure and the difference between max and min. I have the same pump and set mine to work between 2 and 3,5 kg pressure.

 

 

[VocalNeal]

So I glean from this the minimum pressure above the diaphragm should be 2 bar. 

[Crossy]

35 minutes ago, VocalNeal said:

So I glean from this the minimum pressure above the diaphragm should be 2 bar. 

 

With everything off and an outlet tap somewhere open, yes. Pre-charge to 2 bar (30 psi) or so.

[Artisi]

9 minutes ago, Crossy said:

 

With everything off and an outlet tap somewhere open, yes. Pre-charge to 2 bar (30 psi) or so.

Depending on pump model

 

[Artisi]

Crossy, Grundfos tank bladders only replaceable on 60 litre size +

[Paul DS]

5 hours ago, Pogust said:

You can easily set the on/off pressure yourself. Take the lid off the black box on the side, inside you will find the pressure switch. It might even be instructions inside the cover how to do it. You set the max pressure and the difference between max and min. I have the same pump and set mine to work between 2 and 3,5 kg pressure.

 

Yes, I've done that myself in the past!  Very easy.

 

[The Theory]

I hate pumps with pressure tank ????

I love tankless pumps, steady (if pipes size picked correctly). 

Edited March 7, 2021 by The Theory

[xtrnuno41]

I was wondering if the pump has a non return valve itself.

In Artisi's manual it is said in pipework note, it needs a non return valve in the suction of the pump.

The problem exist as from day 1, so it could be  the pump doesnt (included in pump) have that and all water flows back and then everything has to refilled again. So fitting a non return valve in the suction could end all problems. Maybe you have one but it is not working, wrong fitted? If so , see direction of the valve ( should be an arrow on it or so) , if it is fitted right.

Otherwise of course , from day 1, your expansion vessel is not working (broke), a leak inside of that vessel. Ok all was new but never the less it can happen or they didnt give it the right pressure.

Otherwise also could be , your watersystem (pipes in your house, or just anywhere in the outlet of the pumpsystem) has somewhere an air bubble, built up in a pipe. Air is compressible and effects your pumpsystem.

However doubt that is the case, but you never know, could cause problem.   

[3STTW]

Thanks again for all your input. This is my situation as it stands; the current bladder pressure is 2.2 Bar and with everything off the system pressure (at the pump) is 2.4 Bar. When you turn on a downstairs faucet the pressure drops to 1.4 Bar and the pump kicks in, it takes about 5 seconds for the pump to reach 3.2 Bar, then it cuts out and there's a further 10-15 secs before the pump kicks in again.

 

If I do the same thing with an upstairs faucet the whole process takes a lot longer (presumably because of the head pressure).

 

Now, I measured the bladder pressure with my bike stirrup pump so, in reality, it's probably the same pressure that I'm reading from the pump gauge.

 

Here's the tank spec:

 

 

The GT-H manual says this:

 

PRECHARGE PRESSURE The GT tanks are supplied from factory with a precharge pressure. The precharge pressure must be adjusted according to the actual application and the installed pump. It should be slightly below the pump cut-in setting. Recommended precharge pressures: • 0.9 x setpoint for fixed-speed pumps • 0.7 x setpoint for variable-speed pumps

 

That would suggest I increase the 'ON' pressure to 2.44 Bar and reduce the differential so I don't blow out my PVC pipe joints.

 

So I think we may have gotten to the crux of the problem.

 

Any thoughts?

 

 

 

[3STTW]

29 minutes ago, xtrnuno41 said:

I was wondering if the pump has a non return valve itself.

In Artisi's manual it is said in pipework note, it needs a non return valve in the suction of the pump.

The problem exist as from day 1, so it could be  the pump doesnt (included in pump) have that and all water flows back and then everything has to refilled again. So fitting a non return valve in the suction could end all problems. Maybe you have one but it is not working, wrong fitted? If so , see direction of the valve ( should be an arrow on it or so) , if it is fitted right.

Otherwise of course , from day 1, your expansion vessel is not working (broke), a leak inside of that vessel. Ok all was new but never the less it can happen or they didnt give it the right pressure.

Otherwise also could be , your watersystem (pipes in your house, or just anywhere in the outlet of the pumpsystem) has somewhere an air bubble, built up in a pipe. Air is compressible and effects your pumpsystem.

However doubt that is the case, but you never know, could cause problem.   

 

This is not an issue, all the upstairs faucets/showers come on instantly, albeit a low pressure, i.e. there is now draw-down in the system.

Edited March 7, 2021 by 3STTW

[Artisi]

1 hour ago, 3STTW said:

 

This is not an issue, all the upstairs faucets/showers come on instantly, albeit a low pressure, i.e. there is now draw-down in the system.

Looking at the corrosion on the tank, it might be approaching its use by date anyway, could already be a leak developed. 

[3STTW]

52 minutes ago, Artisi said:

Looking at the corrosion on the tank, it might be approaching its use by date anyway, could already be a leak developed. 

That would suggest that the tank was leaking water or air pressure, there's no sign of either.

 

As I mentioned earlier, the 'ON' pressure is way below the tank precharge pressure which is contrary to the manufacturer's instructions and is the likely cause of original surging problem.

 

I'm going to have a crack at it tomorrow and see what happens.

 

[Carlos Primeros]

First of all take off the iron fittings at the pump inlet and check the inside of them. You will be surprised what you will find there. Just look at the attached pictures of my Grundfos pump which I took apart after about 16 years of service. Replace all metal fittings with PVC fittings. And cut the pipes and install unions so you can screw them apart if you need to get to the pump. Now you have to cut them apart. I have opened  up my pump completely and have cleaned it from all the rust and other corrosion. It was a lot of work but at the end the pump and the stainless steel impellers looked like new. All the internal parts in the Grundfos pump are stainless steel. Only the casing is cast iron whith alot of built up corrosion. So I only had to replace the paper gasquets 4 of them for 80 Baht each and the pump was like new. Also the PVC pipes on the pressure side should be 1 " so the waterflow is much better and stronger. And put unions every where where you would have to remove a pump or a pressure tank. So you do not have to cut the pipes and glue them back every time you have to work on them. The Thai workers are just to lazy. They glue everything together. Of course, this is much easier and faster to do. But a hell of a lot of work to take the pipes apart again, if there is some work to do. Look at my pictures of the rusty fittings and valves. And by the way, replace all the metal valves (if you have any) with PVC ball valves (with unions). The pictures speak for themselves.

[JetsetBkk]

10 hours ago, Carlos Primeros said:

put unions every where where you would have to remove a pump or a pressure tank. So you do not have to cut the pipes and glue them back every time you have to work on them. The Thai workers are just too lazy.

 

No, no! It's much more fun to end up with something like this when a valve has to be replaced...

 

 

  ????  

[Carlos Primeros]

Yes, you are right...????. That's  exactly what I meant! nstallations like that are a nightmare...