Another plumbing question!
Discussion
OK so I've just put a new bathroom in and the Mrs choice of fancypants taps for the bath has meant changing the old 22mm fed taps for some that have a 10mm connection at the tap so now the feed goes 22 > 15 > 10. The result is that we now have a dribble coming out of the tap on the hot side. The cold is fine.
Would fitting a shower pump be ok to solve this? Something like this?
http://www.qssupplies.co.uk/bathroom-furniture-sho...
Would fitting a shower pump be ok to solve this? Something like this?
http://www.qssupplies.co.uk/bathroom-furniture-sho...
Can of worms.
It's not really suitable, but would do the job at least for a while. Pumping water through a restriction like that will be noisy and may well overwork the pump a bit. Be warned that Salamander aren't always very happy with honouring warranty claims on pumps fitted outside of their fitting instructions.
The sad fact is that it sounds like you have fitted high pressure taps to a low pressure supply...
It's not really suitable, but would do the job at least for a while. Pumping water through a restriction like that will be noisy and may well overwork the pump a bit. Be warned that Salamander aren't always very happy with honouring warranty claims on pumps fitted outside of their fitting instructions.
The sad fact is that it sounds like you have fitted high pressure taps to a low pressure supply...
Ive got a similar issue, though its not something that Ive done, its been fitted by a plumber...
We had perfectly good flow through a 22mm gravity fed supply into the original mixer on the bath.
We have just had the bathroom gutted and had a thermostat/mixer fitted in the wall, this specified suitable for low pressure gravity fed systems, 0.5bar up.
The original pipes have been blanked and for some reason 15mm pipes fitted to the tstat/mixer from the hot water tank. The mixer has 15mm inlet and outlet, the bath takes a bloody age to fill.
Surely the 22mm pipes (the original bath supply) should have been used up to the 15mm inlets rather than replacing the whole lot with 15mm? Am I wrong in thinking the additional flow rate of the 22mm pipe would increase the pressure through the 15mm fittings or do the simply act as a restrictor?
I read on-line that 15mm pipe needs 4x the pressure to deliver the same flow rate as 22mm.....
We have had a pump fitted to the shower in the on-suite, the plumber is suggesting connecting this to the bath.
I cant see why the damn thing should need it.
We had perfectly good flow through a 22mm gravity fed supply into the original mixer on the bath.
We have just had the bathroom gutted and had a thermostat/mixer fitted in the wall, this specified suitable for low pressure gravity fed systems, 0.5bar up.
The original pipes have been blanked and for some reason 15mm pipes fitted to the tstat/mixer from the hot water tank. The mixer has 15mm inlet and outlet, the bath takes a bloody age to fill.
Surely the 22mm pipes (the original bath supply) should have been used up to the 15mm inlets rather than replacing the whole lot with 15mm? Am I wrong in thinking the additional flow rate of the 22mm pipe would increase the pressure through the 15mm fittings or do the simply act as a restrictor?
I read on-line that 15mm pipe needs 4x the pressure to deliver the same flow rate as 22mm.....
We have had a pump fitted to the shower in the on-suite, the plumber is suggesting connecting this to the bath.
I cant see why the damn thing should need it.
15mm pipe feeds to a gravity fed bath are never going to work well unless you have an unusually large head of pressure feeding them.
The RPD for 15mm pipe is about 7x that of 22mm iirc. Add in the extra equivalent length from every bend and fitting and the problem looks even worse than it might appear at a glance.
Even if the supply pipes were 22mm, the half inch inlets to the mixer are going to noticeably affect your flow rate - despite them being "suitable" for low pressure systems. A case of form over function, presumably due to its wall fitting design?
By the sounds of it, unless you want to rip it all out and start again then you're going to have to run the mixer off the pump as well to get the bath to fill in a reasonable time. A far from ideal situation.
I'm not too keen on the sound of the original 22mm pipework just being capped. Leaving dead legs on a system is a bit of a no no - though it's not always possible to remove it all the way back without making for a lot of expensive extra work.
The RPD for 15mm pipe is about 7x that of 22mm iirc. Add in the extra equivalent length from every bend and fitting and the problem looks even worse than it might appear at a glance.
Even if the supply pipes were 22mm, the half inch inlets to the mixer are going to noticeably affect your flow rate - despite them being "suitable" for low pressure systems. A case of form over function, presumably due to its wall fitting design?
By the sounds of it, unless you want to rip it all out and start again then you're going to have to run the mixer off the pump as well to get the bath to fill in a reasonable time. A far from ideal situation.
I'm not too keen on the sound of the original 22mm pipework just being capped. Leaving dead legs on a system is a bit of a no no - though it's not always possible to remove it all the way back without making for a lot of expensive extra work.
Thanks for that.
Ive just done a rough test, its filling at approximately 6 ltrs a minute... which would equate to (given the details on the website for the tstat, the water pressure equates to being around 0.1 bar.
At 0.6bar it should be 17 ltrs which would be OK I guess - about 6 mins to fill.
Would re-routing the original 22mm pipe up to the 15mm fittings improve the flow sufficiently? Or does the fact the 15mm fittings simply slow it all down?
Its fecking annoying that this has happened - the damn bathroom has cost north of £4k, looks great but the bath takes 20 mins to fill!
Ive just done a rough test, its filling at approximately 6 ltrs a minute... which would equate to (given the details on the website for the tstat, the water pressure equates to being around 0.1 bar.
At 0.6bar it should be 17 ltrs which would be OK I guess - about 6 mins to fill.
Would re-routing the original 22mm pipe up to the 15mm fittings improve the flow sufficiently? Or does the fact the 15mm fittings simply slow it all down?
Its fecking annoying that this has happened - the damn bathroom has cost north of £4k, looks great but the bath takes 20 mins to fill!
It would be better, but by how much I wouldn't like to say for certain, though I'd be pretty confident that it would be significant unless the pipe runs really are very short.
Perhaps phone the manufacturer of the mixer if you know it - they should be able to tell you the flow rates for a given pressure. If you give them the static pressure which would just be the height of the cold tank above the mixer - 0.1 bar per metre. Alternatively you could work out what the dynamic pressure is if you really wanted to here
Alternatively, how accessible is everything? Would it be practical to temporarily connect the 22mm pipe to the mixer via 22mm plastic pipe without creating a lot of work. If you could do that, then it would at least give you a pretty good idea of how limiting the mixer itself is.
6 ltr/min doesn't surprise me - that's exactly what I was getting from the basin gravity fed hot tap on the last bathroom I did (half inch tap and 15mm pipe). The mains fed cold basin tap was a little higher at 25 ltr/min! Fortunately a flow reducer on the cold soon sorted that out.
Perhaps phone the manufacturer of the mixer if you know it - they should be able to tell you the flow rates for a given pressure. If you give them the static pressure which would just be the height of the cold tank above the mixer - 0.1 bar per metre. Alternatively you could work out what the dynamic pressure is if you really wanted to here
Alternatively, how accessible is everything? Would it be practical to temporarily connect the 22mm pipe to the mixer via 22mm plastic pipe without creating a lot of work. If you could do that, then it would at least give you a pretty good idea of how limiting the mixer itself is.
6 ltr/min doesn't surprise me - that's exactly what I was getting from the basin gravity fed hot tap on the last bathroom I did (half inch tap and 15mm pipe). The mains fed cold basin tap was a little higher at 25 ltr/min! Fortunately a flow reducer on the cold soon sorted that out.
With these feet said:
We have just had the bathroom gutted and had a thermostat/mixer fitted in the wall, this specified suitable for low pressure gravity fed systems, 0.5bar up...
No, I'd say LP is 0.1-0.3 bar. 0.5+ is heading for HP territory.With these feet said:
Ive just done a rough test, its filling at approximately 6 ltrs a minute... which would equate to (given the details on the website for the tstat, the water pressure equates to being around 0.1 bar.
So there's 1m height difference between hot water tank and tap - sounds about right. What you've done is fit a high pressure tap to a low pressure system. Change your tap not the pipes 
Simpo Two said:
With these feet said:
We have just had the bathroom gutted and had a thermostat/mixer fitted in the wall, this specified suitable for low pressure gravity fed systems, 0.5bar up...
No, I'd say LP is 0.1-0.3 bar. 0.5+ is heading for HP territory.With these feet said:
Ive just done a rough test, its filling at approximately 6 ltrs a minute... which would equate to (given the details on the website for the tstat, the water pressure equates to being around 0.1 bar.
So there's 1m height difference between hot water tank and tap - sounds about right. What you've done is fit a high pressure tap to a low pressure system. Change your tap not the pipes No wonder we thought it was slow - even the correct low pressure system comes in at 9.1 lpm at .2 bar
Looks like we will simply link in a pump - cheaper than buying and fitting a new stat unit (£240).
Not ideal but should work.
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