Negative Head pump not doing the business

BenEadir · 10-11-2013 11:24AM #1

Hi all,

Here's the story: House was renovated a few years ago. We live in an area with low water pressure. The hot water system had a regular (positive head?) pump installed to power the two upstairs showers and the downstairs bath/shower and it provided a really strong powerful jet of water. I don't know anything about plumbing but this is a summary of our system:-

- Two water tanks in the attic
- New hot water tank (when renovated 4 years ago) in the hot press which is beside one of the bathrooms upstairs.
- Two showers upstairs and one shower/bath downstairs.

One of the upstairs showers (the 'spare/guest' shower which is only used once or twice a week) was always a bit finiky. Sometimes when turned on it would fire up grand but sometimes you'd have to drop the shower head to the base of the shower and shake it to kick start the flow and when that didn't work we discovered that running the hot tap on the bath/shower downstairs would do the trick but only after it had cleared what I assume to be some sort of airlock i.e. it would start slowly, splutter a good bit, build up pressure, splutter some more and eventually get to full flow. this process seemed to kick start things and the upstairs shower would start to flow.

Over the last few months we've had a family member staying to attend college so the affected shower is being used daily and the problem was occurring every single morning needing someone to run the downstairs bath hot tap to get it going but the main shower upstairs always worked perfectly until a few weeks ago when it too acquired the same problem i.e. it wouldn't fire up unless you dropped the shower head and shook it and if that didn't work you'd have to run the downstairs bath hot tap.

I got the plumber who installed the system when the house was renovated back in and he recommended that the existing pump with a negative head pump as there isn't enough natural pressure in the hot water system to start the flow. He's the expert so I went with his advice. the pumps was installed and now things are worse!! Not only does the downstairs bath hot tap have to be run to kick start either shower upstairs but the power from this pump compared to the previous pump is rubbish. It's really weak in comparison.

I don't undertand how a positive head pump was specified 4 years ago and did a pretty good job most of the time and now, with no changes to our plumbing or house layout and no additional showers or anything added, a negative head pump is required. I kind of understand why it may have been an error installing the positive head pump in the first place if the plumber thought there would be enough pressure in the system but it turned out there wasn't but what I don't understand is why installing a negative head pump has actually made things worse!!

I really don't know how to discuss this with my plumber and I'm hoping that some fellow Boardsie here will a) help me understand what might be going on with my how water system and b) give me a few things to say to my plumber or a few questions to ask him???

FYI here are the labels from the newly installed negative head pump which is installed on the ground of the hot press beside the hot water tank.

Appreciate any feedback you guys can give me whatsoever and apologies for the long post.

Ben

corkgsxr · 10-11-2013 11:36AM

Take a picture of the hot press.

oikster · 10-11-2013 11:45AM

Upstairs shower filters,have they been checked?

BenEadir · 10-11-2013 12:56PM

oikster wrote: »

Upstairs shower filters,have they been checked?

I've no idea. I assume (very stupid thing to do I know) that the plumber would have checked basic things like that (I didn't know showers had filters!!) before jumping to the conclusion that an expensive new negative head pump was required :eek:

Where would I find the shower filters? Is is something I could/should have been checking myself? I have a reasonable size aquarium so I'm familiar with the concept of cleaning filters.

Here's some pictures of the hotpress

Ben

oikster · 10-11-2013 02:21PM

Without having seen the shower in question, this will only be supposition but the filters are normally located right at the inlets.Another explanation could be a recurring air lock.Because the flow switches at the pump rely on movement of liquid to actuate, an airlock or blockage would be my best guess.

BenEadir · 10-11-2013 02:30PM

oikster wrote: »

Without having seen the shower in question, this will only be supposition but the filters are normally located right at the inlets.Another explanation could be a recurring air lock.Because the flow switches at the pump rely on movement of liquid to actuate, an airlock or blockage would be my best guess.

Thanks Oikster, really appreciate the input. My amateur instinct is also telling me it's an airlock related issue as running the downstairs bath hot tap, which starts off with just a drizzle and after a minute of spluttering eventually gets a flow going, does kick start the pump which I guess in turn is what gets the upstairs showers going.

My main concerns are:-

1. If the problem was indeed an airlock issue all along (same procedure was needed to get the old positive head pump going) why would the plumber go ahead and install a new negative head pump?

2. How are airlock issues generally diagnosed and addressed?

3. Will the negative head pump eventually deliver a powerful jet of water comparable with the old positive head pump once the air lock issue has been resolved? Are negative head pumps weaker than positive head pumps?

Ben

oikster · 10-11-2013 02:50PM

Because a negative head pump is, ironically, sitting in a positive state when not in use it can sometimes be,believe it or not, the least disruptive solution to a difficult to solve airlock. In your case it seems that there isn't even enough movement to drop the pressure at the pump to bring it on. More in-depth investigation needed I'm afraid.

BenEadir · 10-11-2013 02:58PM

oikster wrote: »

Because a negative head pump is, ironically, sitting in a positive state when not in use it can sometimes be,believe it or not, the least disruptive solution to a difficult to solve airlock. In your case it seems that there isn't even enough movement to drop the pressure at the pump to bring it on. More in-depth investigation needed I'm afraid.

Thanks Oikster, I do like a good puzzle but this one is getting the better of me

Any thoughts on why the new pumps produces such a weak flow compared to the old pump? I assume (there's that dangerous word again) that once the pump is started (whether normally or via the kick start process we are currently having to use) it works normally i.e. it's output isn't restricted in any way?

The other issue I can't understand is why, in a fixed system which hasn't been changed in any way, the pressure goes from being sufficient to start a positive head pump when it was installed 4 years ago to being insufficient now? Are the physics (getting way out of my depth here now) not constant i.e. the hot water tank is in exactly the same location as are the showers etc. What could have changed to reduce the natural pressure to the extent it won't fire up any sort of pump?

Confused.com here

Ben

oikster · 10-11-2013 03:06PM

I'm afraid we are back to partial blockage of the pipework which can be a real challenge to locate and sort.But I would start with the basic stuff pump and shower filters. As a matter of interest do you know where the supply from your hot water cylinder to your pump is taken from. By this I mean from what part of the cylinder. It can be from the pipe coming from the very top of the cylinder or taken from the side of the cylinder about 6 to 8 inches down.Also is there a mixing valve on this line as these also have filters.

BenEadir · 10-11-2013 03:38PM

oikster wrote: »

As a matter of interest do you know where the supply from your hot water cylinder to your pump is taken from. By this I mean from what part of the cylinder. It can be from the pipe coming from the very top of the cylinder or taken from the side of the cylinder about 6 to 8 inches down.

I personally don't know. Here's the top of the cylinder, it has some pipes coming out of it

and here's a picture of the side of the cylinder where there is another pipe coming out about 8-10 inches down from the top of the cylinder. I guess this could be the pipe supplying the pump?

oikster wrote: »

Also is there a mixing valve on this line as these also have filters.

I've no idea I'm afraid

Ben

esox28 · 10-11-2013 04:07PM

Its one of three things or all three, after you've checked the filters.

Reed switch faulty

PCB fautly

flow indicating float getting stuck.

Reed switches and PCB come as a package for around €70 afaik for the 2.0 bar monsoon. Either way you will need to get a compendent plumber or a service call for shower manufacturers.

BenEadir · 10-11-2013 04:17PM

esox28 wrote: »

Reed switches and PCB come as a package for around €70 afaik for the 2.0 bar monsoon.

The 2.0 bar monsoon is literally brand new (a week old) and the problem existed (not as bad actually!!) before the old (still relatively new) pump was replaced so I'm guessing it can't be a failure in the pump.

I probably should have mentioned it before but one thing which could be significant is the fact that when the problem is 'fixed' by running the downstairs bath hot tap until all the air splutters have cleared the showers will then work fine during the day i.e. not only do they start to work immediately but if someone uses the shower that afternoon or evening the pump starts off fine. It isn't until the following morning again when the problem re-occurs. I guess whatever the problem is it takes +/- 24 hours to build up again to the point where it requires the downstairs bath hot tap to be run to clear it again.

What I'm still interested in knowing is why the power from this new pump, once it is engaged, is so much weaker than the previous positive head pump? I think the previous pump was also 2.0 bar but the power felt twice or three times as much. Are negative head pumps always weaker than their positive head equivalents or does that just demonstrate how little I actually know about this subject???

Ben

esox28 · 10-11-2013 04:26PM

if its new just get a warrenty call out from service eng, just to rule out the the problem isent with the pump itself, form what you are saying it also could be the pressure vessel which has deflated and should have been checked by installer on commissioning the pump into operation.

BenEadir · 10-11-2013 04:38PM

esox28 wrote: »

if its new just get a warrenty call out from service eng, just to rule out the the problem isent with the pump itself, form what you are saying it also could be the pressure vessel which has deflated and should have been checked by installer on commissioning the pump into operation.

Thanks esox28, I'll suggest a warranty call out to my plumber.

Can you tell me where the pressure vessel is likely to be located?

Ben

oikster · 10-11-2013 04:40PM

Yes your supply is taken from the top of the cylinder and is protected from air ingress by the fitting used. I am now back to the airlock problem and all I can suggest is that you get your plumber back to see if he can locate the reason for this recurring.

BenEadir · 10-11-2013 04:43PM

oikster wrote: »

Yes your supply is taken from the top of the cylinder and is protected from air ingress by the fitting used. I am now back to the airlock problem and all I can suggest is that you get your plumber back to see if he can locate the reason for this recurring.

Cheers oikster. Enough of this problem. Time to watch Arsenal give United a good old fashioned spanking

I hope neither yourself nor esox28 are united fans :eek:

Ben

esox28 · 10-11-2013 04:49PM

arsenal left it all in europe nothing left, rvp will step up 1 nill united:D

oikster · 10-11-2013 04:58PM

Of course I'm a united fan...........................LEEDS UNITED:D:D:D

BenEadir · 10-11-2013 06:23PM

esox28 wrote: »

arsenal left it all in europe nothing left, rvp will step up 1 nill united:D

Your crystal ball is working quite well so far Esox!!

Ben

esox28 · 10-11-2013 07:57PM

One nill one nill onnne nillll.

BenEadir · 10-11-2013 08:04PM

esox28 wrote: »

One nill one nill onnne nillll.

Well done Esox. My LFC heart always wants to see United lose but my head says its a great result for us. It reels Arsenal in a bit and keeps you lads out of the top four :-) A six point weekend for us!

Ben

oikster · 12-11-2013 08:47PM

One more thing Ben, I wonder were the hoses changed when the pump was changed or are they the originals?

BenEadir · 12-11-2013 11:01PM

oikster wrote: »

One more thing Ben, I wonder were the hoses changed when the pump was changed or are they the originals?

Yes, I think they were.

FYI there is a warranty call into the pump supplier just to rule out there is an issue with the pump.

Regards,

Ben

oikster · 12-11-2013 11:10PM

Just a thought but I heard a story today of a similar problem with the same pump and after FOUR pump changes under warranty the problem persists.The only thing common to any other instances of this,that I have heard of,was the hoses not being changed. Possibility of air intake on the suction hose.

LIFFY FISHING · 12-11-2013 11:51PM

There has Never been four Monsoon pumps replaced under warantee in Ireland ever,as it would never need to be, so thats an urban myth, to confirm the pump is in working order, turn off the water & power to and from the pump, connnect the outlets to two lenghts of qualplex and into an outlet like your bath or shower, and then turn everything on, if the pump pumps and my bet isit will, ur issue is with the plumbing, & 90%of times it iz .

oikster · 13-11-2013 12:03AM

No urban myth LF. These pumps were supplied by Monsoon and I was talking to the man that supplied them and the man that fitted them. You may be right about the Ireland bit but that is all.

LIFFY FISHING · 13-11-2013 09:11AM

oikster wrote: »

No urban myth LF. These pumps were supplied by Monsoon and I was talking to the man that supplied them and the man that fitted them. You may be right about the Ireland bit but that is all.

Rubbish.

If there is a problem with a Monsoon pump its repaired not replaced, & 4 would never be replaced.

oikster · 13-11-2013 09:59AM

I never said that there was a problem with the pumps. I merely told you what I was told. I have seen this problem before and I know that it is not the pump.You do not know the circumstances of the job I was quoting and it was quoted as proof as to the stupidity of some so called suppliers and so called plumbers.

xstevex · 20-11-2013 12:34PM

Sorry for piggybacking on your thread, forgive me I'm new here and I have been following this closely.

Did you sort this problem? I ask because I'm experiencing something similar.

I'm living in an attic bedsit and all taps, shower and cistern apart from the cold in the kitchen are served by a pump located on the floor below.

The cold in the kitchen always has excellent pressure.

Now to the pump.....

The pump for starters only works sometimes ie. its working now with excellent pressure to all outlets however when I turn it the power off from the switch in the flat there is a good chance it wont turn back on when switched back on. In fact oftentimes when I stop running the water through the taps/shower or when the cistern fills and the pump stops pumping it stops working regardless of whether its switched on or not, as if it decided it's work was done.

Yesterday it didn't work at all and when I turned it on I could hear a hum emanating from the pump downstairs but alas no water came.

So in short....

The pump works intermittently.
When it works, the pressure is smashing.
When it doesn't work it hums.
When the power switch is left on when it is working it stops working when i stop running water so when i turn a tap nothing happens.
When not working there is zero flow (negative head?).
The shower head, bathroom sink etc are above all water sources.

Probably unrelated or purely coincidental/imaginary, but it seemed to work perfectly until a lad was round to sort out central heating problems.

I'm confused because it works really well when it works and before I replace it I'd like to discuss it.

Forgive me if reading the above was a pain in the arse.
Any advice would be greatly appreciated.

Thanks and all the best,

Stephen

BenEadir · 20-11-2013 03:05PM

Hi Stephen,

Not sure my experience will be much help.

The original plumber who did all the pipework and fitted the original positive head pump returned and fitted the negative head pump referred to above as he expected that would solve the problem. When it didn't he called out an engineer to service the (brand new) pump. It was fully tested and no fault found.

The problem remains exactly as it was before the negative head pump was installed. The only change is that now once the pump has been kick started by running the downstairs bath hot tap the pressure to the showers is less than half what it was with the original positive head pump fitted.

The other slight difference (to be pedantic) I've noticed with the negative head pump is that when the first shower of the morning is turned on it runs very weakly for about 3-5 seconds, then the flow stops all together and then you have to go downstairs to run the bath hot tap which now starts with a weaker initial flow than before, takes longer to splutter to life (about a minute) and when it eventually reaches its full flow it's only about half the power it was previously with the positive head pump in place.

There's been a lot of scratching of heads going on by my plumber. He fitted everything originally and there's been no amendments to his original pipework so he's proper confused.com. He keeps says "but it shouldn't be doing that" or "a negative head pump should clear that problem".

Next up is a larger negative head pump apparently. That will probably be fitted early next week.

If it fixes the problem I'll report back. Until then the morning process of air lock freeing will continue I'm afraid :rolleyes:

Ben

xstevex · 20-11-2013 07:46PM

Cheers Ben, plenty of head scratching going on here too. Pain in the goolies but I'm sure we'll get there in the end.

Thanks again.

Negative Head pump not doing the business

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