Shower pressure pulses when using hot water

[khunbillmex]

Now that the weather is cooler I've enjoyed some hot showers - well almost enjoyed them. The water is hot enough but the pressure varies as my water pump cycles on off every 15 seconds or so for strong and then off for a few seconds. The temperature doesn’t noticeably change just the pressure. Same happens in the sinks connected to the same heater [a Steible Eltron] when using hot water. When using cold water the pressure is constant  - the pump stays on.  In my kids bathroom which has a different and less expensive heater [a Fujika] this problem doesn’t exist.  When on full hot the pump comes on and stays on. The hot water this heater produces is not nearly as hot as the one in my bathroom. Any ideas on what cause this problem? Any adjustments that can be made? or am I better off just replacing the heater with a better one?  Thanks

[KhunBENQ]

5 minutes ago, khunbillmex said:

The water is hot enough but the pressure varies as my water pump cycles on off every 15 seconds or so for strong and then off for a few seconds.

Can you write down  the model no. of your water pump?

Does it have an attached pressure tank underneath or is there a separate pressure tank.

Water heaters usually have a valve that limits/reduces water flow.

What happens if you open cold water just slightly/half open?

Constant flow?

 

[khunbillmex]

1 hour ago, Arjen said:

I am quite sure with a half open tap the pressure also pulsates. Because the limited flow the pump switches on and off. When there is no restriction, the pump switches on, and never reaches the switch-off pressure.

Hi khunBenq and Arjen

 

The pump is a Hitachi WM-P 250GX2   pdf manual is here: https://www.google.co.th/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwiplbn5zrTRAhVEso8KHZrqCIYQFggqMAI&url=http%3A%2F%2Fwww.hitachi-th.com%2Fhitachi2014%2Fproduct%2Fcatalog%2Fpdf%2FWP_WT-P_WM-P_GX2.pdf&usg=AFQjCNGPpEuPL5Ak6mpUu9os5ZoO7uVAlA

 

It is the pump on the Right side of the manual with the small pressure tank on the Outlet side of the pump.

 

At half throttle half open tap it has the same effect [the pulsating]  Initially it seemed ok as I observed then I thought better actually go check the pump vs watching the water flow. Pump was not coming on at all. I opened the kitchen tap all the way to get the pump to run and then shut the tap off. Back at the shower the pulsating occurred both at full tap open and at half open.

 

Cold water/Half open test  -  pump wouldn't come on.

[CGW]

Drain the pressure tank, the "cushion" required is full of water!

Edited January 9, 2017 by CGW

[eyecatcher]

1 hour ago, CGW said:

Drain the pressure tank, the "cushion" required is full of water!

CGW;  how does that problem generate itself in the first place?....age/air leak/loose screw

[CGW]

^ I've never really thought about "why" it happens!! I have just treated the symptoms as they are very common, 99.9% sure this will cure the problem!  for some reason? over time you loose the air cushion, which is obviously replaced by water! why? need somebody far smarter than me to answer the question - Please I'm gonna guess the answer is quite complex? or maybe I'm dumma than I think..............?

In an industrial scenario the "cushion" would be a bladder filled with nitrogen, if maintained correctly it never fails! answers please......................

Edited January 9, 2017 by CGW

[lopburi3]

Post says the problem is only with connections from a multi point Steible Eltron unit - not with cold water or point of use heater so not sure any normal pump problem.

 

Have never had good experience with those Steible Eltron units in any hotel that I have visited using them (freeze or scalding hot).  Suspect they are designed for higher pressure systems than normally used here.

[Langsuan Man]

I have a Fagor tank mounted in the attic space and have had this problem (pulsing hot water) and after getting rid of my expensive, expansion tank fitted, Grundfos for a normal Hitachi,  the problem did not go away

 

But I did determine that it was only a problem with the inexpensive water faucets  I have.  Any of good ones don't have the problem and the temperature stays stable 

[sappersrest]

Is it only with your shower? Are other taps ok,if so clean strainer on shower inlet pipe and clean shower head.

[Langsuan Man]

1 hour ago, sappersrest said:

Is it only with your shower? Are other taps ok,if so clean strainer on shower inlet pipe and clean shower head.

 

Both, shower and faucets, and as previously stated the good ones have no problem it is the "off" branded ones that I will eventually have to replace

 

Master bathroom does not have this problem, only the guest bathroom, so head and inlet pipe is not the problem 

[khunbillmex]

8 hours ago, sappersrest said:

Is it only with your shower? Are other taps ok,if so clean strainer on shower inlet pipe and clean shower head.

No    it also occurs at the double vanity sinks connected to the same heater If I go full hot on one sink it will occur. IF I open taps on both sinks given the reduced water flow it does not occur.

[bankruatsteve]

37 minutes ago, khunbillmex said:

No    it also occurs at the double vanity sinks connected to the same heater If I go full hot on one sink it will occur. IF I open taps on both sinks given the reduced water flow it does not occur.

 

It sounds like your multi-point heater is the issue.  Are there any adjustments that can be made on the heater that make sense?  

[BEVUP]

Have the same problem, Have one in the bedroom top floor & the first thing was to remove all the fine filters. Have 225 Mitsu pump & have to drain tank maybe every 4 mths.

The Pvc run is maybe 20 mtrs ground level with maybe 4 or 5 bends then rises maybe 6 mtr to head of the standard 3/4 i think

I did look at pump specs of various models & i think it should of been the next size up but they seem to put the 225 in all Moo Baans

Am going to play with it at some stage as i reckon i could P harder 

[khunbillmex]

I think I may have discovered the culprit: I was looking over the wiring schematic and noticed something called the Water Temp Relay.From this site ( http://www.bkwater.com/index.php/en/product/water-pumps.html ))  it states:

Water pumps Hitachi Model WTP - The tank, made of thick stainless steel, is durable, clean, safe and rust-free. - The motor comes with heat ventilating fan and thermal relay to prevent the motor from overheating. - Water Temp Relay temporarily pauses the operation when pump head becomes too hot. This prevents pump head from deforming through overheating.

[RichCor]

1 hour ago, khunbillmex said:

- The motor comes with heat ventilating fan and thermal relay to prevent the motor from overheating.
- Water Temp Relay temporarily pauses the operation when pump head becomes too hot. This prevents pump head from deforming through overheating.

This usually shuts off power to the motor until the metal cools (lasting 10's of minutes).

 

 

On 1/9/2017 at 3:38 PM, khunbillmex said:

At half throttle half open tap it has the same effect [the pulsating]  Initially it seemed ok as I observed then I thought better actually go check the pump vs watching the water flow. Pump was not coming on at all. I opened the kitchen tap all the way to get the pump to run and then shut the tap off. Back at the shower the pulsating occurred both at full tap open and at half open.

 

Cold water/Half open test  -  pump wouldn't come on.

This post doesn't quite make sense to me.  What do you mean, "pump wouldn't come on"?  

Did the water just trickle to a stop?  Could you clarify this?  

I'm wondering what occurs at other water taps when flowing water at 25%, 50%, 100% flowrate for a period of time, vs the same on the shower (with temperature mixed, or pure HOT at 25%, 50%, 100%) ...when/where does the water flow pulse. 

 

My well pump can consistently feeds 3 open taps, with only very minor waterflow/pressure changes being noticed when the pump cycles on to refill the system.  So a working system shouldn't be pulsing ...unless the pressure switch is adjusted too low (and the bladder tank empties out before the pump cycles back on to recharge it).

 

[khunbillmex]

On 1/24/2017 at 11:43 AM, RichCor said:

This usually shuts off power to the motor until the metal cools (lasting 10's of minutes).

 

 

 

 

Yes that makes sense. I wondered why would the pump overheat just after turning on and how could it cook itself so fast.

 

This post doesn't quite make sense to me.  What do you mean, "pump wouldn't come on"?  

Did the water just trickle to a stop?  Could you clarify this?  

 

I think there is city water pressure as well.  After turning on the 2nd floor shower I came downstairs to check the pump. The pump was not operating* although water was flowing out of the shower head  at what seemed a reasonable volume before I went downstairs.. To increase demand I went into the kitchen and turned the tap on. The pump then started. I  then turned the tap off and observed the pump . It began doing its on off dance.

              * it seemed off  - not just taking a pause when it on/off cycles.

 

A neighbour just told me that this is a common problem with "on demand" pumps and he suggested I replace it and get a pump with a reservoir.

[RichCor]

2 hours ago, khunbillmex said:

I think there is city water pressure as well.

 

OK, so you may have a 'pressure assist' pump.

 

Some caution is due here, as directly coupled pumps on outside water supplies are illegal, and potentially dangerous -- as they 'draw' water in they can create a negative pressure on the water mains, stealing pressure from other users on the line, and possibly allowing contaminants to be sucked into the feed via reverse flow. 

 

The standard method of augmenting water pressure from an outside water source is to add in an additional large capacity water tank connected to its own pressure pump, in parallel to your mains water system, with appropriate backflow prevention one-way valves, as described in many forum posts here on ThaiVisa...  such as:

 

Installing water pump
Started by GavinK, July 3, 2013

 

Check the posts and responses by member @Crossy

 

Quote

It's not rocket science to set up one of the all-in-one pumps. It should already have the necessary one-way valve to stop losing pressure back to the tank.

Hook it up something like this:

The non-return valve gives you city water pressure when the pump is off for maintenance or you have no power.

 

Quote

Normal operation leave all the valves open.

If the power is off, once the pressure reserve is depleted, city water flows through the non-return valve and supplies the house. There is a non-return valve built in to the pump inlet that stops back flow through the pump.

Close the two pump valves if you need to remove the pump for service.

 

[khunbillmex]

PROBLEM FOUND/SOLVED  Sometimes things have to get worse before they get better. Last week the shower changed from its 15 sec pulse routine to every second. I had removed the shower head before and cleaned it [it was pretty clean to start with]. This time I also removed the chrome arm.  There was a pressed in place metal water saver/flow restricter disk at one end. I bought a new shower head with an arm whose tube was unrestricted [399thb] Magic -problem solved after all this time.  Thanks to everyone here for suggestions . In this case it seems we should have applied Occam's razor first.