Simplest and cheapest way to try to balance it is to put an isolator valve in the cold supply to the mixer. You can get really cheap push fit ones operated by a screwdriver (google 15mm isolator valve). You can then turn it a little at a time to limit the flow from the cold side so it isn't overpowering the hot.
There is a difference between pressure and flow, so I can't promise it will definitely work, but it's the cheapest and simplest, and it doesn't hurt to have an isolator valve there.
In fact you may already have one, if so, try closing it down an then opening it a whisker at a time
If you can't get more hot water from the boiler then you have to limit the cold.
That's exactly why I've kept my hot water cylinder rather than going combi.
Del

Thank you for your suggestions. I think there is something behind the hot/cold valve plate on the bathroom wall where you can adjust something up to a point. Not sure it was an isolator valve though and we did try it but to no avail. We're trying to avoid removing the plate if at all possible.

The chappie who fitted the bathroom is popping round in an hour or so to put in the pressure reducing valve where the mains water comes into the house but, as mentioned before, I don't know how low to turn the mains pressure down to (it's measured in bars on the reducer valve gauge). Any suggestions on that?

Yep, the water is plenty hot enough elsewhere.

The bath and all the fittings are brand new and decent ones - the mixer tap and valves are Crosswater. That's not to say they couldn't be faulty but I'll try the other ideas first before going back to the supplier.

What was your other idea then as to the cause?

I had a similar experience with my new shower control.

There was a "scald protector" inside.

I had to remove the handle then the facia plate and there was a lever to adjust how hot "hot" was.

I don't remember the make or model of the control.

HTH......

Yep, similar control inside our shower and the troublesome bath mixer tap. Making the hot hotter sorted out the shower but not the bath tap.....

Just put in a Pfister in the bathtub and it had something similar; a plate that governed how far to "hot" the valve could turn. We had to adjust it to "all the way to hot, thanks."

I'm with you on this GameJudge. The very exact thing happened with my new Delta....once the plastic adjuster that is around the mixer stem was changed to allow the handle/valve to swing to the farthest "hot" setting (lefthand, counterclockwise to full hot) the problem was immediately solved.

I have $20 saying that this is the required fix (as I have stated above and in a previous posting), and not a boiler or delivery/service hot & cold piping swap problem/installation error.

Ours is the same. When installing the valve I had only the cold turned on to check for leaks on the cold side and the "shuttle cock" inside jammed up so when I turned on the hot to test there was nothing flowing. Turned off the cold water line and the pressure from the hot line freed it up. Took a while to get the balance right with the adjustment after that but it works fine now.

Another possibility, since it new something got into the hot water line during installation. It's now lodged in the hot water port of the mixer.

Ah, that would explain what happened to the guinea pig...

Only joking. Yep, thanks, there's always a chance of that. Will keep that in mind especially if we end up having to take off the wall plate.

Maybe not the guinea pig but he could have left something behind that could have done it. Let's just say a few less droppings in it's cage.

You'll never fix things without taking 'em to bits.
The trick is to try to anticipate problems, be methodical, don't force things, use the right tools and most of all, recognise when you don't know what you are doing and stop.
Conversely don't be afraid to have a go.
As long as you know how to turn off the water supply the worst that is likely to happen is you get a bit wet.
Put a cover over the shower drain so you don't loose any screws you take out.
If the guy fitted a mixer he should have left you with the instructions that go with it.
Del

That was my thought too. Chunk of solder or glue washed into the tap. Combine that with a scald restrictor and you will have NO hot water.

I'd stick with the hot and cold faucet control, those mixing valves suck...

1/ How far from the water heater is your bathroom? The draw off may be too much if it is too far or the heater is too small.

2/ What size hot water pipe has been run? Often (and yes, I am a licensed plumber) plumbers go with a standard 1/2" for hot water. not correct depending upon your answers in item 1.

3/ Considering both items 1 & 2 are all good, has the hot water pipe been lagged correctly? Heat loss over a long draw off, plus a smaller water heater with a low recovery rate = cold baths/showers.

The solution is all dependant upon the person who did the pipework. I would call this person and have him/her check the problem, sometimes it's as simple as thread seal tape blocking the inlet to the tap. Either way - you paid for a new bathroom, you should not have to pay anything so soon to have it repaired, nor should you have to install additional components to make things work.

Good luck on getting a good result, my fingers are crossed for you

If you study the path the hot and cold follow, I suspect that the hot line has a greater pressure drop - is more restricted.

That means you need to restrict the cold tap so it is capable of the same maximum flow rate as the hot. I suggest a valve in series with the cold to throttle it.

Measure the time to flow 20 liters of the hot and set the cold throttle to the same.

This will give the automatic valve two equal pressure streams to control

We have mixer taps and have no problem with hot/cold pressure differential unless perhaps your water pressure is very low - I understand that most mixers do not work well with gravity feed systems, however there are mixers specially designed for very low water pressures. Alternatively something is blocking the hot water flow at the mixer - and that could be a 'scald protector' - some of these feed cold water in with the hot to lower its temperature to the 'pre-set maximum allowable temperature' which is defined by legislation........ this may be built into the tap design.......

Do some research of the tap make and model you have had fitted.

Another alternative is that perhaps during installation the plumber inserted a plug - rag or paper into the H/W line to keep rubbish out of it while he was doing other preparation work, and then forgot to remove the obstruction when he was connecting the lines ..... don't laugh, it has happened more than once and it has happened to good, experienced plumbers ..... It is not a frequent occurrence but it does occur, and is more likely if he gets distracted during the job.....

Can't see why you have a problem here. If you have had the shower fitted get the fitter back. Its not your problem and as soon as you start meddling you will stuff any warranty.

Firstly, a nice friendly, balanced and interesting Blog.

I agree with the ones saying something is probably wrong with the hot supply or the hot side of the mixer, it could even be an airlock if pressure is not high......the advice (assuming no other problems) to turn the cold pressure down with an isolator is good advice from several posters.....Del was the first if I remember correctly, I would have done the same....

The OP did not tell us if the mixer was fitted with a thermostat or not to keep the temperature stable. In fact, I personally would never buy a mixer for the bath/shower that did not have a temperature control built in. In our house, using the toilet while someone was showering would result in screams as the hot got too hot. Fitting a thermostatically controlled mixed has fixed that problem completely....such cold water uses now go completely unnoticed....

As an aside, why is it that many countries (UK for example) still have seperate taps for hand basins and baths/showers? You either freeze or cook, the plug is usually missing to make things even worse..

We have only mixers in all bathrooms and toilets in our house. Nowadays they do not cost much more than taps.......here anyway, and they work really well.....

If it is a theromstatically-controlled mixer tap, are the hot and cold pipes connected to the correct ports on the tap?

I'm mightily impressed with all these sensible and helpful suggestions - thank you so much.

Am meeting the original fitter later this week as he is keen to sort it out too and so I will go through all these suggestions with him.

BTW, yes, it has a thermostat somewhere in the mixer valve which we previously turned up to hottest but that didn't do the trick.

Thank you again,

Bosunbabe

Anonymous 19 is probably right. Hot and cold feed are swapped. And just about the easiest thing to check.

$20 says the incoming pipes are crossed over.

Excellent point, you may have hit the button on the first try!

OOOOH! Good one! That would make a mixer cold ALL the time. Our bath has separate taps but they were hooked up hot on the right and cold on the left and so if it can happen with two separate taps, then it certainly could happen with One mixer tap.

Just to clarify......if the hot and cold pipes had been fixed the wrong way round would the water be cold all the time, then??

If so, that would eliminate that possibility because the water is warm all the time - neither hot enough for a hot bath but nor can you draw cold out of it either. The temperature of the water out of the mixer tap doesn't seem to vary much, however much you twiddle the hot/water lever back and forth.

Tell us whether or not the pipes are the wrong way round. I've got $20 riding on it!

I've got another $20 that says it doesn't matter.

If the water is lukewarm or tepid all the time regardless of the handle setting...

Something is wrong with the mixer. See #2.

TWENTY BUCKS!

Most Com bi boilers run off the mains, so the pressure of the hot and cold should be the same, the flow rate is the thing to look at, there is a flow rate measuring cup that will tell you the rate,I'm sure you could hire one, there not very expensive to buy so I'm sure that the hire cost would be minimal,If you find the cold is much higher than the hot check the inlet and outlet on the boiler to make sure they are fully open,then check a tap nearest the boiler ( one that isn't a mixer ) and see what the temperature is like, there should be a temp control on the boiler so if the temp at the tap isn't hot enough alter the temp, normally to make the water hotter in a comb ie you are reducing the flow rate this gives the water longer in the boiler to heat up,If you have to reduce the flow too much then that is why the mixer won't deliver, See if you can reduce the flow to the cold side of the shower valve. I've never liked comb ie boilers, they can never deliver the same amount of hot water, what Ive done in the past is to fit motorized valves in the heating side, one for heating & one for hot water then get a mains pressure hot water cylinder,hook it up to the heating side then use the comb ie hot water to feed the sink in the kitchen, you will need someone who is qualified to wire in the valves and cylinder.

Although I agree the hot water pressure from a combi tends to be higher than the UK is used to with its old header tank systems the hot pressure from a combi must always be less than the cold water pressure. You have to get pressure drop through the heat exchanger.

Surely the other system you suggest is just the pressurised storage system. More expensive than a simple combi but far better and gives you the option to install an immersion for when the combi croaks.

I have been using Comb Boilers for at least 26 years. Boilers with hot water tanks are generally far less efficient due to heat losses......never store hot water.....

The one fitted when we bought the house did not deliver enough hot water for a REAL shower, luckily it was on its last legs and we replaced it with a far bigger one, problem solved.

In my limited expoerience, you need at least 27KW of heating power to get a good reasonable flow of hot water for showering and bathing, more is of course even better......

It turns out therefore that our heating boiler is larger than a plumber would fit for our small house, so rooms warm up real quick in winter....great!

I have also fitted oversize rads in every room over the years and a now our fully insulated house has made a) The heat up speed is fantastically fast b) rooms stay warm a very long time, rads are usually cold as the heat stays in the room, c) Remote control thermostats that sense the temp required where you are in the room has made the whole package REALLY attractive.

It has also reduced our heating costs per year dramatically since we moved in.....we are paying less for gas and wood pellets combined than we did for gas alone for 26 years.....not even accounting for the real value of the money today in comparison to then.......DM1,800 per year against €600 (DM1,200) per year now.

I was unable to find some way of converting the currency from 1986 to the currency of today. If we say its value is only 50%, THEN I am paying only around DM600 per year....half of what I was paying in 1986.....wow!(1DM to 1€ = 2 to 1)

agree - a combi has to be cheaper than stored - but

with stored you get the option to put a solar coil in so thats free heat and of course its not lights out when the combi goes cos you can have an electric immersion heater.

I've got combi boilers in my rental properties and a real system in my own. Heat losses from the tank are no where as bad as they used to be and of course in the winter they are helping to warm the house.

You say never store hot water, well I have a condenser boiler with a mains pressure cylinder that holds 410liters of water, we have two bathrooms and one cloak room,we can use both bathrooms at the same time & not deplete the hot water, Recently the boiler packed up so I had to turn on the immersion heaters & I found that after a day the water was so hot that I shut off one of the heaters the water stayed hot so I turned off the remaining heater at midday,The next day I forgot to turn it back on but we still had plenty of hot water & I found that I could turn It on for 5 hrs every other day and still have baths or showers as per normal. the cylinder is highly insulated stainless steel mains pressure, so storing hot water dose work.

Bazzer

Other than the good point about it being more difficult to use Solar energy (but not impossible) to heat water, the losses are still there.

Solar energy can be still used if done carefully, you use it to heat a water storage tank. No immersion heaters (unless you want to have an emergency backup) for example, but you feed this as the cold water feed into the combi boiler, so it either has no work to do and switches off it's heating, or it has only to add a little bit of heat energy to get the required temperature.

That way you are only storing "free" heat (wel almost!), and reducing your combi boiler usage.....you could even turn the combi boiler off in the summer if you are able to get enough water for daily usage at the temperature required..... My boiler still lets the cold water through when switched off, but I am not sure that all Combi Boilers will allow that......just the ones I have seen and used.

If you had enough heat/quantity of hot water in the tank, you could even add a coil and push the water for the rads through it to get some low quality heat in the house on those days when it is simply too cold to sit indoors (like here two Saturdays ago, I turned on the pellets burner for 4 hours.....)

I have never personally done it, but that could be the best of both worlds. What do you say?

This past spring we redid the kid's bathroom including the installation of a new tub, shower wall surround, and a Delta shower/tub mixing valve w/ all the necessary plumbing that goes with it.

The Plumber forgot to adjust the plastic anti-scalding "disk" that was behind the wall cover and handle, which fit around the mixing valve. For a week I tried everything to get more hot water out of it. The best I could do was get tepid water. Yet, I was able to get lots of hot water from the new bathroom lavatory faucet! This naturally drove me bonkers until I downloaded the Owner's manual from the Delta website and then discovered that the installer had to adjust the mixing valve plastic disk!

Problem easily fixed in 5 minutes! [And I'm not a plumber either!] Saved some Big $$$$ by doing myself......

Problems like this is exactly why permits should be required and inspections made when the job is complete. A lot of good answers, but I would go with crossed connected piping or an restriction in the hot side piping. Check your local code on what what the required temperature should be.

YAR

"Check your local code on what what the required temperature should be."

Please cite the code section where this might be found. The local code for anywhere on the planet would be just fine.

As there's money on the outcome I'll get back to you once it's fixed ..... thanks again for all suggestions, it's been an education for me!

Bosunbabe

bosunbabe

Shower plumbing

Ging a little sideways:

My Son inlaw had a Large pump fitted to enable hime to run two showers at once; worked a treat so when I had some Bathrooms improved here used that trick as well. Showe has gone from Marginal to Excellent/Superb - only my Gym has better flow!

Son in law had some work done which included a new boiler ; pump was taken out by the plumbers. Result very poor showers which can no longer cope with more than one shower at a time.

Why, the new boiler is a combi boiler and the Cold water is starved by an inadequate pressure and flow on the cold water line. he is currently stuck there.

Is there a possible thought here for bosunbabe?

Sleepy

That sounds like a bad plumber to me. I have seen such work done here in Germany.

To fix, you need to use the largest diameter pipe possible from the water supply to the combi, even if you have to reduce down to go into the combi and large again from the combi to where the water will be used, the two showers for example.

Some stupid plumbers actually use much too small a gauge of copper pipe, only 15mm for example....when he should be using 22mm at least, even bigger is better of course. All long runs must be of a large diameter.....

Also, you need to see how many KWs the combi has, for two showers I would personally recommend at least 50-60KW or more......if its smaller than 50 and two showers are run together, you will see the problem described, even with a pump.....to get the flow better, you must turn down the required temperature....

Also, someone should check that all isolator valves are fully open, minus 1/2 turn back (to allow movement in both directions after years of non usage), and also be at least the size of the pipe being used.....don't forget the emergency cock, sometimes outside of the house.....it gets turned off for work to be done and sometimes its forgotten to open it fully again.

Andy

The cold water pipe dia is governed by the pipe coming in from the road, the boiler is too close to where the pipe lands for the internal pipe to make a significant difference. i believe that the incomer is the standard nominal 1/2"

This coupled to the pressure of the water and it's variations(!) are enough to cause the problem. agree that IF there was sufficient water pressure and IF the Water Company would supply a larger pipe for a reasonable cost - then that would be a way forward.

On Isolator valves I had not discussed this with him- or his various plumbers! But as the balance seems OK and I have used two of the showers - then i cannot see that it can be an Isolator poblem - but I could be wrong!

I am sure that the Stop Cock has been checked ad nauseum and there has ben too little time since the system was built for problems to develop.

I would just bung a pump back in if it was my house! That way everyone can have an acceptable shower without people yelling across the hopuse, the water's gone cold!

Thanks very much for the input.

The other solution is to bung a 2" incomer in from the mains!!

I understand that the Water Company charges arms, legs and lots of other bits for that!

I believe that the Boiler is adequately sized but I do not have the numbers too hand.

Sleepy

You wrote:-

I believe that the Boiler is adequately sized but I do not have the numbers too hand.

Sleepy

The question is, "who sized the boiler?" If it was the plumber, they have tables of size of houses, nuber of bedrooms, style of building..... ad nauseum. These tables always supply boilers and rads that are too small for comfortable living.

Some boilers, if you are lucky, can be upgraded to a higher KW with replacement of some parts.

Using my own 27KW combi as an example, it will only feed one shower well, certainly not two, my wife may not even agree that one is fed adequately as she likes it really hot..........

So simply put, you need at least 50KW for adequate hote water for two showers, or you go to a hot storage tank, fed from the central heating circuit of the combi and running all the year round, but with an isolator to stop heating the rads in summer.

Andy

I note your advice on kW requirement (50kW) and will pass that on.

My own Boiler is about *kW, not Combi, and feeds two showers more than adequately.

** i cannot find the label at this time! And it's time to eat - will try to get back.

Thanks for the information

Sleepy

I installed one of these with the "scald protector" (mixing valve) in it and found that there was a "burr" inside one of the passages left from manufacturing. Had to disassemble the the entire valve to fix it by cleaning all the passages of left over mfg junk!

Do you have a 'better half' to try it first ?

Never in my life have I found a shower that works. Either frozen or broiled. It's oft suggested that a shower is more 'eco'. Rubbish. By the time you've adjusted it, the atlantic has gone down the plughole. After all that twiddling you've wasted a bunch of water. A relaxing bath is far better.

Film fans will know Clint Eastwood in a bathtub. Nuff said.

I remember Clint in that film, always had his six shooter poking out of the water!

We best keep quiet about such stuff