"Oi stop using the taps, I'm in the shower!"

[ATV]

Newbie to DIY here

I'm sure everyone's shouted this at some point during their lives. You're having a shower and some inconsiderate git starts doing the washing up. Or else you're gagging for a tea and need to fill the kettle up but some inconsiderate git has banned you from using the taps until they've finished their 45 minute shower.

If I was doing a full renovation project, is there anything I could do to run separate pipework to prevent this? What do I need to ask for from the trades?

Thanks

[OldGermanHeaps]

We used to have that same problem until we fitted mira mode electronic showers. Now running any other taps in the house makes zero difference.

[Countdown]

ATV said:

Newbie to DIY here

I'm sure everyone's shouted this at some point during their lives. You're having a shower and some inconsiderate git starts doing the washing up. Or else you're gagging for a tea and need to fill the kettle up but some inconsiderate git has banned you from using the taps until they've finished their 45 minute shower.

If I was doing a full renovation project, is there anything I could do to run separate pipework to prevent this? What do I need to ask for from the trades?

Thanks

Do you have a Combi boiler which feeds all the hot water taps? That's what we used to have in a previous house and that's exactly what used to happen.

I think replacing a mixer shower with an electric shower might fix the issue (short of installing something like a megaflo)

[Sheepshanks]

Countdown said:

I think replacing a mixer shower with an electric shower might fix the issue (short of installing something like a megaflo)

We have a pressurised hot water system but the old electric shower in one of the bathrooms still freaks out - flow drops a lot so temp shoots up and can cut out - if someone fully opens a tap or (worse) flushes a toilet. The other (non-electric) shower isn't so affected but the flow to it does slow but it adjusts its temperature to keep it constant.

I think to seamlessly cope you'd need something like a water accumulator, which holds up the pressure when demand increases.

[sherman]

If its just a standard 3 bed house with 1 bathroom a slightly overspecced combi boiler will easily cope with your requirements.
If you work out you need a 25kw just order the 30kw boiler. It wont be much more expensive.

[OutInTheShed]

Many combi boiler systems have a pressure regulator valve either on the feed to the boiler or the feed to the whole house.

This may be more of thing in hilly places, where the mains pressure can be several bar, combis often want no more than 3 or 4.

With such a system. you could take the feed for an electric shower from upstream of the PRV, it might want its own PRV?

Our cheapo thermostatic mixer shower seems reasonably immune.
Both hot and cold to the shower seem to come from the regulator valve, so they vary together.

[Mont Blanc]

sherman said:

If its just a standard 3 bed house with 1 bathroom a slightly overspecced combi boiler will easily cope with your requirements.
If you work out you need a 25kw just order the 30kw boiler. It wont be much more expensive.

Yes, or alternatively fit a properly specced pressurised system boiler with a 300 litre unvented/pressurised cylinder like I did.

Hot water delivered at full mains pressure all over the house, and it will keep delivering hot water even if you filled 2 full baths at the same time and then immediately ran 2 long showers. We've probably never come anywhere near to running out of hot water.

Someone turning on a hot (or cold) tap anywhere in the house makes no noticeable difference to the hot water flow or the temperature of a running shower.

[PhilboSE]

It all depends on the hw system type.

For a combi, you can go up on the kw rating of the boiler, but if your mains water pressure or flow aren’t adequate then you’ll still get the same issue and it’s hard to overcome.

For unvented systems you can have an accumulator installed before the hw tank which can make a big difference.

For vented systems it is really a case of making sure you have big enough tanks, and 22mm minimum primaries feeding water around, and decent pumps for thermostatic showers.

I have a house with extremely poor mains water pressure AND flow. We can have 3 showers running concurrently at a steady 3bar, but the solution to give this is horrendously complicated!

[Mr Pointy]

sherman said:

If its just a standard 3 bed house with 1 bathroom a slightly overspecced combi boiler will easily cope with your requirements.
If you work out you need a 25kw just order the 30kw boiler. It wont be much more expensive.

Not necessarily true. If the incoming flow & pressure can't support the combined draw the boiler will just cut out on overheat if it can't modulate low enough.

[OutInTheShed]

PhilboSE said:

It all depends on the hw system type.

For a combi, you can go up on the kw rating of the boiler, but if your mains water pressure or flow aren’t adequate then you’ll still get the same issue and it’s hard to overcome.
.....

There are two 'issues'.
One is the flow varies due to other loads on the system
The other is that the temperature varies.

Mostly you can live with a fair bit of the first issue, if the second issue is sufficently controlled.
If you've got a half-decent thermostatic mixer and the hot and cold pressures vary together, it will probably be OK.
If you've got a thermostatic electric shower, it should be OK within limits.

So long as it doesn't die to a dribble or blast you out of the bath, a bit of variation in flow rate can be survived.
Being scalded or frozen, not so much!

Our previous house was dead simple.
Main shower over the bath was from a gravity tank system.
T'other shower (electric) and the kitchen sink tap were off the mains.
That was absolutely fine, so long as you didn't go mad with one of the other hot taps while someone was using the main shower.

[Sheepshanks]

OutInTheShed said:

Our previous house was dead simple.
Main shower over the bath was from a gravity tank system.
T'other shower (electric) and the kitchen sink tap were off the mains.
That was absolutely fine, so long as you didn't go mad with one of the other hot taps while someone was using the main shower.

Where did your toilet cisterns refill from? In my parents house, they were from the water tank, so no issue (but they did take a while to refill).

Every house I've ever lived in, even with a cold tank in the loft, the toilet cisterns have refilled directly from the rising main. It's when the toilet is flushed that we can get issues with the electric shower.

[smokey mow]

ATV said:

Newbie to DIY here

I'm sure everyone's shouted this at some point during their lives. You're having a shower and some inconsiderate git starts doing the washing up. Or else you're gagging for a tea and need to fill the kettle up but some inconsiderate git has banned you from using the taps until they've finished their 45 minute shower.

If I was doing a full renovation project, is there anything I could do to run separate pipework to prevent this? What do I need to ask for from the trades?

Thanks

Replace the mixer taps with a thermostatic mixer, you’ll still loose pressure if someone turns on another tap but at least the temperature will stay the same in the shower.

[rossyl]

Look up MegaFlo. Specifically unvented hot water tanks, and a system boiler combination.

You can have multiple showers at once.

Also, the pressure at wash point will be significantly better.

[GAjon]

On my house , the incoming pipe with the stopcock is 3/4”.
I modified the pipe work after the stopcock and made a small 3/4” manifold with two 1/2” branches, one picked up the existing feed to the house , the other I ran a dedicated pipe too the electric shower.

That was 24 years ago, never had a problem with flushing toilets, kettle filling or washing machine starting affecting the shower flow.

[drmike37]

As above, you need a proper pressurised system with a big water tank. Ideally with its own boiler for full PH overspec points.
We have managed to get to the end of our hot water, but only when we had 12 people living in it for the weekend.

[malaccamax]

rossyl said:

Look up MegaFlo. Specifically unvented hot water tanks, and a system boiler combination.

You can have multiple showers at once.

Also, the pressure at wash point will be significantly better.

We have an unvented tank. Flow still slows when someone uses water elsewhere, eg flushes a loo. V annoying.

[Countdown]

malaccamax said:

We have an unvented tank. Flow still slows when someone uses water elsewhere, eg flushes a loo. V annoying.

IANAP but the only time we've noticed a pressure drop is when one of the kids is having a shower / bath as well AND my wife's running the taps in the kitchen. it was something that was quite important to us when we moved from a 1 bathroom house with a combi boiler and a mixer shower

[blueg33]

Megaflo or similar.

Usually an easy install onto the current system

[Road2Ruin]

With a combi, which this sounds like, making sure the incoming flow is up to scratch is a good idea. We then had a 22mm ring main for the water, which then meant the cold and hot weren't competing with each other. We can have multiple outlets on, with very little, if any, noticeable drop.

[paulrockliffe]

Both a well specced Combi and an Unvented system can easily be flow-limited; if the incoming supply is 12l/min and you like your shower at 12l/min then both will behave exactly the same when someone opens a tap.

If you have an unvented system you can flow that 12l/min at tank temperature, ie very hot, so you can get heat out of all the taps and the shower at once without the shower going colder, but still at 12l/min across everything. A good combi will do the required temperature rise to give you a very hot trickle of water out of the shower too, a smaller one might not. If the water coming in is 24l/min then either system can manage the OP's requirements easily enough.

With an unvented system you can side-step low-flow with an accumulator, but otherwise neither approach will do what the OP wants unless the incoming mains is capable of supplying the water fast enough. So the first step is to measure the flow-rate and then take it from there.