shower mixer pressure woes

[sem]

Trying to install a shower mixer for bodjets, and wanted the main shower to be on at the same time. Plubmed in a non-return valve no problem, but when I switch on, i'm getting very poor pressure performance from the whole thing. This is strange to me as I have a mains pressure cylinder.

I am using 1.5m flexihoses up to the shower - could this be the problem or should I try something different.

Any advice would be welcome.

 

[bathjobby]

Flexihoses always give significantly reduced flow rates. Just take a look at the inside diameter of the pipe (not the fitting) and you will see why.

 

[ChrisR]

What's the mains pressure? What's the cylinder you have; integral expansion space (like Megaflo) or a separate pressure vessel?

ALso, add up the flow rates - compare totals depending on which outlets you use.

 

[sem]

Wow - thanks for the fast replies.

The cylinder is a non-vented tribune premier (180 litres) which says it has an operating pressure of 3 -3.5 bar.

from 15mm copper, I have added two 1.5m flexihoses. Through one mixer then via 15mm copper to 4 body jets and then via a double check valve to the overhead shower.

 

[ChrisR]

Ah. The pressure will be the LOWER of the mains pressure and 3 -3.5 bar. so it could be , er 1 bar.

Yours is the separate pressure-vessel type too (I think), so you don't have the entirely fortuitous pressure-reserve of some types. Do you have a loft?

How long are the 15mm pipes?
What make is the mixer/contrivance thingy? Do you have any tech info on it?

You need to measure what the heck's going on. Measure those flow rates in litres per minute with all open (add em up). Also measure the flow at the kitchen COLD tap and tell us, then open the garden tap as well
and measure them both, telling how far apart they are. (Sounds daft - just trying to do it in one hit).
Then buy a water pressure gauge - about £12. Measure the P at the garden tap with no others flowing, then open the kitchen tap to give say 10 litres per minute and record pressure.

Hope you can see what I'm driving at. If your mains supply is poor, you may have to do something radical to get a good shower. Is the unvented cyl new installation? Did the installer have certificate to show competence?

You won't like this bit : do you still have a big ol' cistern in the loft?
How would you feel about a pump?

Is the shower head fixed? If so I don't right now see why you need a dcv. Might be wrong about that though..

 

[sem]

>> Yours is the separate pressure-vessel type too (I think), so you don't have the entirely fortuitous pressure-reserve of some types. Do you have a loft?

Yes it has a pressure-vessel in the airing cupboard.
Yes I have a loft with small expansion tank in it, but no water tank.

>> How long are the 15mm pipes?

The 15mm pipes are about 7m long (before the flexi-stuff that I have added).

>> What make is the mixer/contrivance thingy? Do you have any tech info on it?

I don't have any information other than it is a 3 way valve unit with BANYO written on the temperature knob.

>> You need to measure what the heck's going on. Measure those flow rates in litres per minute with all open (add em up). Also measure the flow at the kitchen COLD tap and tell us, then open the garden tap as well and measure them both, telling how far apart they are. (Sounds daft - just trying to do it in one hit).
>> Then buy a water pressure gauge - about £12. Measure the P at the garden tap with no others flowing, then open the kitchen tap to give say 10 litres per minute and record pressure.

This will take me some time to do !!

>> Hope you can see what I'm driving at. If your mains supply is poor, you may have to do something radical to get a good shower. Is the unvented cyl new installation? Did the installer have certificate to show competence?

The cyl is about 7 years old, and gives strong performance to the other three showers in the house - just not this new one with the body jets working,

>> You won't like this bit : do you still have a big ol' cistern in the loft?
How would you feel about a pump?

I am ok with a pump, but didn't think that I could put one on a mains based system - is there such a thing ?

>> Is the shower head fixed? If so I don't right now see why you need a dcv. Might be wrong about that though..

There are three different shower heads and all three are (now) less than satisfactory. The vari-head single head system it replaced did not seem as poor - but I could be wrong about that !

 

[chrishutt]

I don't have any information other than it is a 3 way valve unit with BANYO written on the temperature knob.

Which of these is it?

Why am I the only one with the initiative to use Google?

 

[bathjobby]

Christ you guys and ChrisR, all good stuff, BUT, flexihose has a significant reduction on flow rate due to its reduced internal diameter over copper 15mm or 22mm.....
However, I suggest you ignore this again and buy some more water pressure gauges, consult more people for the answer you are prepared to accept (rather than the obvious) and continue in your quest for your answer.....

 

[sem]

I don't have any information other than it is a 3 way valve unit with BANYO written on the temperature knob.

Which of these is it?

Why am I the only one with the initiative to use Google?

It is nothing to do with those

It is more like http://www.banyo.co.uk/details/VALVEKIT-8333.html but a 3 mixer rather than a 2. I have already searched google, yahoo and MSN and been unable to find the exact same one.

 

[sem]

Christ you guys and ChrisR, all good stuff, BUT, flexihose has a significant reduction on flow rate due to its reduced internal diameter over copper 15mm or 22mm.....
However, I suggest you ignore this again and buy some more water pressure gauges, consult more people for the answer you are prepared to accept (rather than the obvious) and continue in your quest for your answer.....

Thanks !

I am open to any legal suggestions

Actually, I am currently replacing the flexihose with copper and retesting prior to borrowing a pressure gauage (if still required).

 

[ChrisR]

I'm not saying flexy hoses aren't resistive, but do the sums - how much head are you losing on a metre of flex? Couple of metres? Then how would that affect the flow on the mains which has already come down a lot of 15mm - not too much. Don't forget all the flow on a single shower goes up a long flexy..!


Next take the flexies off the back of the shower and run them into a bucket - see how the flow rates compare.
Next take the heads off and see if the holes are just a bit small!

I've checked a few mixer valves recently and found some to be very resistive. As your other showers are Ok then it isn't the rather over-common poor mains supply causing the problem, at least. The comment about a pump could have been a solution - use tank in loft as a reservoir and pump your cylinder up to 3.5 bar.

Would be interesting to know those flow-rates!

 

[bathjobby]

Christ ChrisR, you sure know how to make something as difficult as possible. For gawds sake, Flexi's significantly reduce flow rates.....

 

[ChrisR]

[code:1]Flexi's significantly reduce flow rates.....[/code:1]
Please quantify...!

I'm not arguing that it matters! Depends on those internal diameters - some are 10mm.

Sure they do matter if it's a gravity supply - but it's mains! it doesn't matter much about a shower hose diameter on an electric shower. You have to do the sums! You'll be losing a maybe a couple of metres head on say 30 metres head, so maybe there's 10% loss. I was more concerned about whether the pressure was 1 bar or 3 bar

At 25 l/min you lose about 1metre head per metre run in 15mm. So that adds up. The flexies and the pipe are the cheapest to change so use 22m (plastic is fine), and at least 15 where the flexies are.

 

[sem]

Christ ChrisR, you sure know how to make something as difficult as possible. For gawds sake, Flexi's significantly reduce flow rates.....

Swapped over from Flexi to 15mm Copper and it made a good difference, but still not enough for the body jets to operate effectively.

Is there any kind of pump I can get that will not require a water tank in the loft ?