shower pump not providing good pressure of hot water

[alexg]

i have a new techflow negative head twin-ended pump for supplying a shower (on the same floor as the hot water tank) and a loft bathroom.

when the pump was fitted, i also had the techflange fitted to the tank (drilled in to the side of the tank, approx 3/4 of the way up the tank).

the pump should supply ample water pressure to my thermostatic shower, but for some reason, the hot water supply is only a fraction of the cold supply... as the pump evens out the pressure, when running the shower at a comfortable temperature, the flow is pretty rubbish... when running it cold, the pressure is much much better.

the connections to the tank are 22mm as per the techflow instructions and the pump starts and stops as it should.

any ideas as to why the flow of hot water is so derisory?... could it be due to the location of the flange (towards the top, as opposed to lower down)?

i know that with the techflange, the warranty is increased to 3yrs, which i presume is down to the positioning of the flange in the tank (ie. picking up less scalding hot water, thereby increasing the lifespan of the seals), but tbh, if this is the reason for the waterflow issue, i might have it changed so i can actually enjoy a decent shower.

cheers

 

[alexg]

any ideas?

 

[Richard C]

Not without more information on the system design & a schematic diagram would be great!

Where is the cold water storage tank location that feeds the shower/bathroom?
Does this also feed the hot water cylinder or it there a separate cold header tank for that?
What is the distance from the pump outlet to the showerhead & the loft bathroom?
What is the maximum pump head?
Is the problem just on the shower or is hot flow restricted in the bathroom also?
Are you sure it’s not just a fault with the shower mixer valve?

The “Techflow” flange is nothing more than an “Essex flange”; its location in the cylinder can be misleading because there is an upturned pipe inside which should terminate near the top of the cylinder, it's use is not designed to restrict water temperature, did someone tell you it was? The pump manufacturer’s warranty extension for using the flange is usually concerned with prevention of aerated water (which damages the pump impeller) & not the water temperature. Excessive water temperature can also damage the pump (usually restricted to 60 degrees) but positioning the flange lower down the cylinder (if that’s what’s been done) is not good & is not a guaranteed way of restricting the temperature, this should be done using a Thermostatic Mixer Valve (TMV)l but it's not causing your problem.

 

[alexg]

Not without more information on the system design & a schematic diagram would be great!

Where is the cold water storage tank location that feeds the shower/bathroom?
Does this also feed the hot water cylinder or it there a separate cold header tank for that?
What is the distance from the pump outlet to the showerhead & the loft bathroom?
What is the maximum pump head?
Is the problem just on the shower or is hot flow restricted in the bathroom also?
Are you sure it’s not just a fault with the shower mixer valve?

The “Techflow” flange is nothing more than an “Essex flange”; its location in the cylinder can be misleading because there is an upturned pipe inside which should terminate near the top of the cylinder, it's use is not designed to restrict water temperature, did someone tell you it was? The pump manufacturer’s warranty extension for using the flange is usually concerned with prevention of aerated water (which damages the pump impeller) & not the water temperature. Excessive water temperature can also damage the pump (usually restricted to 60 degrees) but positioning the flange lower down the cylinder (if that’s what’s been done) is not good & is not a guaranteed way of restricting the temperature, this should be done using a Thermostatic Mixer Valve (TMV)l but it's not causing your problem.

thanks for that Richard.

i have a seperate header tank right up at the very top of the eaves (approx 8ft above and 6ft laterally away from the hot water tank)

the issue is with the shower immediately adjacent to the pump. the pipe from the pump descends below the floor, passing across the door threshold and up in to the shower.

there is no apparent problem with hot water pressure supplied to the loft bathroom... this is located above and approx 12ft laterally away from the hot water tank.

the pump is a qt80nhe-2 which operates at up to 2.3 bar. this goes to a 4" watering can head.

does this help?

thanks

 

[Richard C]

i have a seperate header tank right up at the very top of the eaves (approx 8ft above and 6ft laterally away from the hot water tank)

Am I right in assuming this cold water storage tank feeds both the hot water cylinder & the cold water inlet to the pump?
Is the h/w cylinder new or existing? Is it vented?

the issue is with the shower immediately adjacent to the pump. the pipe from the pump descends below the floor, passing across the door threshold and up in to the shower.

So, the h/w tank is on the same floor as the shower but on the floor below the bathroom?
Where is the pump in relation to the hot water cylinder & how & where does the pumped supply tee off to go to the shower & the loft bathroom?
Is the feed pipe work to the shower mixer all in 22mm?
Is the shower feed pipe work new or was some existing?
Have non restricting “full bore” shut off valves been used on the shower circuit? Fitting ordinary service valves or gate valves will restrict flow!

there is no apparent problem with hot water pressure supplied to the loft bathroom... this is located above and approx 12ft laterally away from the hot water tank. the pump is a qt80nhe-2 which operates at up to 2.3 bar. this goes to a 4" watering can head.

Has the problem been there since install? If so, have you considered calling whoever installed the pump & pipe work back to sort it out?
Are you absolutely sure there isn’t just a problem with the shower mixer valve?
Why have you fitted a negative head pump when you don’t appear to have a negative head system? Not that it should make a difference!

As you can imagine, it's quiet difficult trying to visualise how your system is plumbed without a schematic diagram. It may help to check your installation against the pump manufacturer’s installation guide here:
http://www.techflow.co.uk/qtinstall.htm

 

[alexg]

i have a seperate header tank right up at the very top of the eaves (approx 8ft above and 6ft laterally away from the hot water tank)

Am I right in assuming this cold water storage tank feeds both the hot water cylinder & the cold water inlet to the pump?
Is the h/w cylinder new or existing? Is it vented?

the issue is with the shower immediately adjacent to the pump. the pipe from the pump descends below the floor, passing across the door threshold and up in to the shower.

So, the h/w tank is on the same floor as the shower but on the floor below the bathroom?
Where is the pump in relation to the hot water cylinder & how & where does the pumped supply tee off to go to the shower & the loft bathroom?
Is the feed pipe work to the shower mixer all in 22mm?
Is the shower feed pipe work new or was some existing?
Have non restricting “full bore” shut off valves been used on the shower circuit? Fitting ordinary service valves or gate valves will restrict flow!

there is no apparent problem with hot water pressure supplied to the loft bathroom... this is located above and approx 12ft laterally away from the hot water tank. the pump is a qt80nhe-2 which operates at up to 2.3 bar. this goes to a 4" watering can head.

Has the problem been there since install? If so, have you considered calling whoever installed the pump & pipe work back to sort it out?
Are you absolutely sure there isn’t just a problem with the shower mixer valve?
Why have you fitted a negative head pump when you don’t appear to have a negative head system? Not that it should make a difference!

As you can imagine, it's quiet difficult trying to visualise how your system is plumbed without a schematic diagram. It may help to check your installation against the pump manufacturer’s installation guide here:
http://www.techflow.co.uk/qtinstall.htm[/QUOTE]


thanks again for your reply...

the hot water cylinder is existing from before... in the previous installation, i had it connected to a salamander ct50 twin-ended pump and it worked fine... as for whether it's vented... i have no idea? how would i establish this, and what is the significance?

the pump is immediately adjacent to the hot water tank at the base of the airing cupboard. both the cold water supply and the hot water from the tank enter via 22mm connections.

the shower feed pipework (for both hot & cold) is smaller than 22mm though and is the original (which once again, worked fine beforehand)

there are gate valves fitted to both hot & cold feeds to the pump, but as i mentioned in the original post, there doesn't seem to be an issue with cold water supply via the pump, and this has exactly the same valve and pipe setup to the hot.

i guess there could be an issue with the shower valve... i'm just trying to cut down on the possibles before calling in the fitter or calling up the supplier of the shower valve...

the system requires a negative head pump as the top floor bathroom is above the level of the main cold water tank (but slightly below that of the header tank)... erring on the side of caution, i went for the negative head to ensure that there were no issues with supply to this bathroom... iirc, the pump automatically senses whether it is working as a positive or a negative head and adjusts to suit, so the worst case scenario is that i've forked out for a better pump than i need?

the only other thing to throw into the pot is that sometimes the water pressure when running at normal temperature begins fine, but slowly begins to drop... does that indicate anything?.... (a lack of vented hot water cylinder, issue with the header tank etc etc?)


thanks

 

[steve32]

are gate valves existing or new.
remove hot inlet supply to pump and check flow (gate valves do break may not be fully open)

 

[alexg]

are gate valves existing or new.
remove hot inlet supply to pump and check flow (gate valves do break may not be fully open)

the gate valves are new, but that wouldn't explain how the water pressure can begin to drop as the shower runs... ?

 

[steve32]

are hot and cold correctly fitted to shower valve.
most faults I find are h & c crossed or blockage in pipework.

 

[steve32]

switch off power to pump
switch on shower will shower get hot on max hot, run for few mins
or is shower running warm, cold only or no temp dif
post back reply

 

[Richard C]

After doing most of the donkey work I seem to have been hijacked ! As Steve now seems to be so very keen to get involved, I’ll leave you in his hopefully capable hands!