Bath filler from thermo mixer - 15mm or 22mm?

[silverhornet]

I am about to connect the pipework to a new thermostatically controlled 3 way mixer - with 2 showers and 1 bath filler.

The inlets for the hot and cold are both 15mm as is all the pipework in the flat - the flow rate is 18L/min for cold (mains fed) and 9L/min for the hot from the combi boiler (which is 5 feet away).

My question is what diameter pipework should I be fitting to the bath filler?

The outlet from the mixer is 1/2 female so I am assuming it should be 15mm but is this enough for a bath? The distance from the mixer to the filler is about 1.3m of pipwork (wall mounted mixer and combined overflow and spout halfway down the side of the bath).

I was going to fit 15mm polypipe and pushfits but would like some advice from those in the know.

I will be fitting DCVs and service valves on the hot and cold feed into the mixer, which will restrict the flow so is 15mm acceptable or should I be looking to increase pipe diamter where possible - i.e. 22mm DCVs and a 22mm connecting pipe from mixer to filler (even though both ends are geared towards 15mm as they have 1/2" threads which again will rectrict flow)?

Any constructive advice welcome.

 

[gas4you]

Don't know all the answers to your questions, but 15mm to the bath filler is normal when the hot is from a combi. The difference in flow between the hot and cold may give problems with the showers. Did they come with a flow restricter to put in the cold?

I take it that as you are getting only 9 l/min hot that you have a 24Kw combi? Shame you havent got a more powerful one with your good flow rate.

Others on here will be able to answer other questions better.

 

[Dan Robinson]

Should be fine; although if the mixer has built in check valves I wouldn't bother with extras. Just make sure that you use full-bore service valves and not sh1tty ball-a-fix ones.

 

[silverhornet]

I contacted the supplier/manufacturer of the mixer and they told me it didn't come with a check valve (although having said that, I had to explain what they were) - however there are small plastic fittings in each inlet which looked like valves - white nylon cup around a spherical insert.

Now this may not be the correct way of checking, but I blew into the outlets and there was no air coming out of anywhere after a slight click so I assumed there were in fact check valces inside so I proceeded to fit the cold fed.

Rest assured in true DIY fashion I decided to turn the cold on without having connected the hot. How I laughed........with a floor or cold water out of the hot water inlet. At least I've left enough room to retro fit the DCV tomorrow so I guess the manufacturer was correct - no check valve, or at least none that seem to work.

I always fit the full size ball valves instead of the small ones....at least I was able to turn the water off! Anyway, at least the cold fed joints are holding.

For the record I fitted a 15mm polypipe to the outlet for the bath and the rate is v close to that from the kitchen tap - so cold is kicking out about 18L/min.

Is it worth fitting a restrictor or just closing the ball valve on the cold until I get the balance I want?

In any case, thanks for the reassurance that the 15mm is ok.

 

[Dan Robinson]

Leave it and see if it copes - if it is thermostatic then you shouldn't have any problems as the pressures are equal.

 

[silverhornet]

Hmmm. Connected the hot pipe and unless I practically close the cold lever valve the cold pressure seems to be preventing the hot from flowing.

Not good. Any suggestions as to how I can get at least some cold and more hot as I need to have the temp on hotest and the lever valve on the cold is less than 45 degrees (more like 20 degrees with fully closed being 0) and you can hear the pipe hissing as the flow is being restricted..

I have positioned the DCV after the lever valves which in turn are about 1m of pipe from the mixer as I have positioned them so they can be accessed from under the bath. Would moving the DCV closer to the mixer make any difference? the pipework for both hot and cold are identical.

I'm a little frustrated now as I paid a handsome price for the mixer and although it looks nice......it doesn't seem to be delivering the goods.

Could it be a high pressure tap and I have low pressure, although I thought combis generally delivered high pressure? It's so bad at the moment that I would consider a different mixer whilst the stud workwallis still exposed.

 

[jay1]

have you thought about using a pressure equalising valve?

dont know if it will work as i havent used one before but maybe someone else on the forum has.

http://www.plumbworld.co.uk/344-0000

 

[Dan Robinson]

Pressure is the same, it will be the flow that is the problem if it is not the mixer itself.

http://www.arrowvalves.co.uk/productdetail.php?id=1

A 9 or 10 litre/minute might help.

I am surpised that this is a problem though.

What make and model shower is it? Are you 110% sure that the hot and cold feeds are going into the right ports?

 

[silverhornet]

good point and no with regards to the ports.

How do you tell whih is hot and which is cold? I worked on cold - right, hot left? bit of a pain if wrong - will contact the supplier to check which way the ports go.

However, (he said) although no instruction whatsoever, there were two small round plastic objects which I have no idea what they are for although they seem to fit into the inlet ports. They appear to restrict flow and have only a very small opening (they sort of look like sparklers for beer pumps).

The mixer is a Sagittarrius - EL.277/C ERGO CONCEALED SHOWER VALVE WITH 3WAY DIVERTOR (abouth half way down on the right)

http://www.sagittarius.ltd.uk/html/shower_valves.html

 

[Dan Robinson]

They would be flow restrictors. It might be an idea to remove the hot one.

Check the casting fdor an H or C, or even the words. Sometimes there is a coloured dot over the corresponding port.

Your flow rates with them too.

 

[silverhornet]

Having checked there are indeed casting on the valve and thankfully I had the hot and cold the right way round and I had not fitted the restrictors to either inlet.

I spoke to Saggittarius and they will be sending me replacement valve inserts (plastic gubbings which act like a single check valve) to see if this helps.

Strange thing is that the showers work fine and get hot and have plenty of power whereas the bath needs to be on the hottest setting with the cold practically off?

If that wasn't enough I dropped one of the handles which has now dented the bath....wouldn't be so bad but i was putting a blanket in the bath to stop such an accident......nevermind.

 

[Dan Robinson]

Check you flow rate when running the bath. It may be too high hence the low temperature.

 

[TicklyT]

Check the casting fdor an H or C, or even the words. Sometimes there is a coloured dot over the corresponding port.

Bear in mind where the mixer was made - e.g. the French and Italians use 'C' for hot (= chaud or caldo)

 

[ChrisR]

Strange thing is that the showers work fine and get hot and have plenty of power whereas the bath needs to be on the hottest setting with the cold practically off?

Not strange, really.

We all shower around 38-40, and a hot bath is about 45.
Most combis have flow restrictors in them to limit the HW flow such that the temperature is OK for a bath in the dead of winter, when the mains is only a few degrees. Some are precise but others aren't, and will let too much water through, which is therefore too cool.
So, it varies a bit, but you expect to need the cold supply to the mixer off, or pretty near it.

 

[silverhornet]

A big thank you to everyone.

Well the current mixer is now redundant and a new one is on its way. the hot water is now a trickle and thankfully the supplier is sending a direct replacement - so although the first mixer seems to be at fault after trying every conceivable connecting and re-connecting the supplier has come through so fingers crossed I'll have running water this weekend......

Watch this space and again thank you for your advice and guidance.